58413929 Ansys CFX Mesh Tutorials

CFX-Mesh Tutorials

CFX-Mesh Tutorials

Table of Contents

Introduction to the CFX-Mesh Tutorials List of Features Legal Notices

Tutorial 1: Static Mixer Introduction to CFX-Mesh Geometry Creation Geometry Modification Mesh Generation

Tutorial 2: Static Mixer (Refined Mesh) Modifying the Mesh Generation

Tutorial 3: Process Injection Mixing Pipe Geometry Creation Mesh Generation

Tutorial 4: Circular Vent Geometry Creation Mesh Generation

Tutorial 5: Blunt Body Geometry Creation Mesh Generation

Tutorial 6: Butterfly Valve Geometry Creation Mesh Generation

Tutorial 7: Catalytic Converter Geometry Creation Mesh Generation

Tutorial 8: Annulus Geometry Creation Mesh Generation

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CFX-Mesh Tutorials

Contents•Copyright

CFX-Mesh Tutorials

Tutorial 9: Mixing Tube Geometry Creation Mesh Generation

Tutorial 10: Heating Coil Geometry Creation Mesh Generation

Tutorial 11: Airlift Reactor Geometry Creation Mesh Generation

Tutorial 12: Room with Air Conditioning Geometry Creation Mesh Generation

Tutorial 13: Can Combustor Geometry Import Mesh Generation

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Introduction to the CFX-Mesh Tutorials

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The CFX-Mesh Tutorials are a set of tutorial examples which demonstrate how to set up the geometry and mesh for a variety of different problems. The tutorials cover most of the meshing functionality available in CFX-Mesh together with some of the most commonly-used geometry features from DesignModeler. Each example results in the creation of CFX-5 GTM file, which can be imported directly into CFX-Pre. You will find instructions for setting up CFD simulations using these meshes in the CFX-5 Tutorials which are part of the main on-line help for CFX-5.

Some of these tutorials require the use of Parasolid files (for geometry import). If you have not already obtained these files, they should be readily available from the CFX Community Website: go to http://www.ansys.com/cfx and follow the Community link. This site is available to all registered CFX users. If you have not already got a username and password, go to http://www-waterloo.ansys.com/cfx/community/apply.htm to apply.

The tutorial instructions are based on ANSYS Workbench 8.1, although they will contain notes when instructions would have been different in the previous version. If you still have an earlier version of ANSYS Workbench then you may be able to find tutorial instructions explicitly for that version on the CFX Community Website using the link above.

If you want to print out the tutorials, then we recommend that you follow the link to the CFX Community Website to download a package in pdf format, and use this for printing.

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CFX-Mesh Tutorials Home List of Features

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List of Features

List of Features

The following table shows you which geometry features are covered in which tutorial.

1 2 3 4 5 6 7 8 9 10 11 12 13

Sketching Mode

Draw Toolbox • • • • • • • • • • •

Modify Toolbox • • • •

Dimensions Toolbox • • • • • •

Constraints Toolbox • • • •

Settings Toolbox • • •

3D Features

Extrude • • • • • • • • • • •

Revolve • • • •

Sweep • •

Skin/Loft •

Other Features

Parasolid Import • •

Multiple Bodies • •

Freeze/Unfreeze/Add Frozen[a] • • • •

Body Operations[b] • • •

Plane Creation from Faces[c] • • •

Imprint Faces[d] • • •

Enclosure •

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Contents•CopyrightIntroduction to the CFX-Mesh Tutorials> List of Features

List of Features

[a] Freeze/Unfreeze/Add Frozen: for multiple bodies and for creating bodies which enclose another body

[b] Body Operations: for copying, moving, and subtracting bodies from other bodies

[c] Plane Creation from Faces: for 3D Feature operations on existing surfaces

[d] Imprint Faces: for Boundary Condition Surfaces

The following table shows you which meshing features are covered in which tutorial.

1 2 3 4 5 6 7 8 9 10 11 12 13

2D Region Groups • • • • • • • • • • • •

Face Spacing[a] • • • • • •

Curvature-Sensitive Meshing • •

Controls[b] •

Periodicity

Inflation[c] • • • • • • • • • • •

Stretch •

Proximity[d] • • •

Preview Groups[e] • • • • •

Full Surface Mesh Generation • •

Parallel Volume Meshing

[a] Face Spacing: for refining the mesh on a particular face or faces

[b] Controls: for refining the mesh near a point, line or triangle

[c] Inflation: for producing prism elements along a boundary in order to resolve the boundary better

[d] Proximity: for refining the mesh when two faces or two edges are close but not joined

[e] Preview Groups: for previewing part of the surface mesh


List of Features

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Legal Notices

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Contents•CopyrightIntroduction to the CFX-Mesh Tutorials> Legal Notices

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List of Features Home Tutorial 1: Static Mixer


Tutorial 1: Static Mixer


This example shows geometry creation and meshing for a simple static mixer. It assumes that you have never used ANSYS Workbench before and gives detailed instructions on every step needed to construct the example. The following geometry and meshing features are illustrated:

● basic geometry creation including Revolve and Extrude operations; and ● basic meshing operations.

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Legal Notices Home Introduction to CFX-Mesh

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Introduction to CFX-Mesh

Introduction to CFX-Mesh

In order to create a mesh using CFX-Mesh, the steps are as follows.

1. Create the Geometry. 2. Define Regions. 3. Define the Mesh Attributes. 4. Create the Surface Mesh (this is optional).5. Create the Volume Mesh.

You can create the geometry either in ANSYS Workbench or by importing it from a CAD package. The geometry creation tool in ANSYS Workbench is DesignModeler, a parametric feature-based solid modeler. Most of the CFX-Mesh Tutorial Examples include instructions on creating geometry in DesignModeler, although for full documentation you should consult the DesignModeler Help.

The remaining four steps are all carried out within CFX-Mesh. The creation of the surface mesh is optional; if it is not created explicitly, then it will be generated as part of the creation of the volume mesh.

ANSYS Workbench helps you to manage all of the files created by DesignModeler and CFX-Mesh by the use of the Project Page. Your first step after opening ANSYS Workbench will be to create a new project, and by returning to the Project Page (which is available at any point during your ANSYS Workbench session) you can switch between DesignModeler and CFX-Mesh, add new files to the project, and so on. We recommend that you create each new project in a new directory so that all the files for each project are kept separate. You can also then run the CFX-5 software from the same directory after generating the mesh.

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Tutorial 1: Static Mixer Home Geometry Creation

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Contents•CopyrightTutorial 1: Static Mixer> Introduction to CFX-Mesh

Geometry Creation

Geometry Creation

Creating the Project

The first step for any new case is to create the project.

1. Open ANSYS Workbench. On Windows, this can be done by going to the Start Menu and selecting Programs>ANSYS 8.1>ANSYS Workbench. See below for instructions if you are still using ANSYS Workbench 8.0.1.

2. Start a new project from scratch by selecting Empty Project from the New section of the Start window in the middle of the ANSYS Workbench window. (Depending on which modules are available, you may find that you need to scroll down to see Empty Project icon.) The Project Page will appear, containing Unsaved Project.

3. The next setting is to tell ANSYS Workbench where you want your project files to be created. Select File>Save, and save the project as StaticMixer.wbdb in a new directory of your choice.

You can then open DesignModeler in order to start creating the geometry.

1. At the left side of the Project Page, click on New geometry (under Create DesignModeler Geometry). 2. In the popup window, select Meter as the desired length unit.

If you are using ANSYS Workbench 8.0.1, then instead:

1. Open ANSYS Workbench by going to the Start Menu and selecting Programs>ANSYS 8.0.1>ANSYS CFX CAD2Mesh 2.1.

2. Create a new project by selecting Create a new project from the left-hand side of the ANSYS Workbench window.

3. The main part of the window will now show a series of questions and settings to initialize the project successfully. The first question is What do you want the new project to initially contain?. This tutorial will create the geometry from scratch, so select the answer Nothing - I will build this project from scratch.

4. The next setting is where you tell ANSYS Workbench where you want your project files to be created. In the Name: box, type StaticMixer as the name of the project. In the Location: box, browse to find the name of the directory in which you want to keep the project, e.g. G:\CFXMeshTutorials\ on Windows systems, or /home/user/CFXMeshTutorials/ on UNIX systems. (The actual directory name you enter will depend on where you would like to store the files on your system.) Turn ON the option Create a subfolder based on the project name;.

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Contents•CopyrightTutorial 1: Static Mixer> Geometry Creation

Geometry Creation

5. Now click on Open the Project Page to create the project.

6. At the left side of the Project Page, change the Length Unit: to Meters using the drop-down list. Then click

on Create DesignModeler Geometry.

Back To Top

Overview of DesignModeler

Once DesignModeler opens up, you will be able to see four main areas to the window.

● The Model View displays the geometry. The geometry can be manipulated using the mouse buttons. For example, holding down the middle mouse button and moving the mouse over the Model View will rotate the geometry. Clicking the right mouse button over the Model View will bring up a menu which includes various options for manipulating the model as well as other options which are particular to what geometry operation you are performing or what objects are selected. To put the model into a particular view, you can also use the Triad which is displayed at the bottom right corner of the Model View: click on one of the axes or on the cyan-colored ball to move the model. You can zoom out to view the entire model by right-clicking over the Model View and selecting Zoom to Fit. You can zoom in to a selected area by clicking with the right mouse button and dragging the mouse over the required area whilst holding down the button.


Geometry Creation

● The Details View shows the details for the selected object. No object is selected when DesignModeler is first opened, so it is blank in the picture above. It can be used to edit the details (including the name of the object) by simply typing over the information to be updated.

● The Tree View shows all of the features of the geometry, and their states. When DesignModeler is first opened, only the three default planes (XYPlane, ZXPlane or XZPlane, and YZPlane) are present, together with an entry which shows you that there are currently 0 Parts, 0 Bodies. As you perform geometry creation operations, the structure of the tree will expand to show these. The geometry operations such as Extrude and Revolve are applied from the top of the tree downwards. For example, in the tree shown below, Extrude2 was the first operation, followed by Revolve2.

The symbols next to the operations and features indicate their status:

Symbol Meaning

Everything is OK.

The item is suppressed i.e. not taking any effect (it can be unsuppressed later).

Something is wrong with the item e.g. you tried to generate it before you had fully specified it, or you modified one of the features above it which makes the specifications of the item invalid. (You can see the error messages by right-clicking on the object and selecting Show Errors and Warnings.)

The item needs to be generated or re-generated (because changes to the settings have been made since it was last generated).

The sketch will remain visible even when not selected.

The Body has been hidden (made invisible).

● The top part of the window contains the various menus and toolbars.

DesignModeler has two main modes of operation, and you will have to switch between them as you build up your model. In Modeling Mode, the Tree View is shown, as in the picture above. However, DesignModeler uses sketches (collections of edges in a plane) to build up solid models, and to create these sketches, you need to be in Sketching


Geometry Creation

Mode. To switch between the two modes, the tabs (Sketching and Modeling) at the bottom of the Tree View are used: simply click on the appropriate tab to switch between the two modes.

The area which is occupied by the Tree View when you are in Modeling Mode is taken up with the sketching toolboxes (Draw, Modify, Constraints, Dimensions and Settings) when in Sketching Mode. To switch between them, simply click on their names.

Back To Top

Recovering from Mistakes

You are certain to make mistakes as you build up your geometry, so it is important to know how to recover from these.

If you are in Sketching Mode, then the Undo button in the Undo/Redo Toolbar towards the top of the window can be used to undo sketching operations. The Back button (accessed by right-clicking over the Model View) can be used to undo the selection of (for example) the last point in a polyline, whilst sketching.

If you are in Modeling Mode, and you have not yet generated your feature (such as Extrude) you can either just make further changes in the Details View, or you can delete it by right-clicking on its name in the Tree View and selecting Delete.

After generating a feature, you can delete it by selecting it in the Tree View and using the Delete on the right mouse menu. If you have generated a feature e.g. Extrude and then realize (for example) that you selected the wrong sketch to define it, you will need to use the Edit Selections feature. This is accessed by selecting right-clicking over the name of the feature in the Tree View and selecting Edit Selections: you will then be able to edit the selections by using the Details View as usual.

Back To Top

Creating the Solid

You need to start creating the Static Mixer geometry by creating a sketch to make the main body of the mixer.

1. Click on ZXPlane in the Tree View towards the top left of the screen. [If you are using ANSYS Workbench 8.0.1 then instead click on XZPlane; the plane normal is then reversed.]

2. Click on the Sketching tab (underneath the Tree View) to work on the sketch.

Each sketch is created in a plane. By selecting the ZXPlane immediately before going into sketching mode, you ensure that the sketch you are about to create is based on the ZXPlane.

Before starting to create your sketch, it helps to set up a grid of lines on the plane in which the sketch will be drawn.


Geometry Creation

The presence of the grid allows the precise positioning of points (when Snap is enabled).

1. Click on Settings (in the Sketching tab) to open the Settings Toolbox. 2. Click on Grid and turn ON Show in 2D and Snap. 3. Click on Major Grid Spacing and set it to 1. 4. Click on Minor-Steps per Major and set it to 2. 5. You now need to zoom in to see the effect of changing the Minor-Steps per Major. Click the right mouse

button to the top left of the plane center in the Model View and drag a box across it to zoom into the middle of the grid. When you release the mouse button the model will be magnified to show the selected area.

You now have a grid of squares with the smallest squares being 50 cm across. Because Snap is enabled, you will only be able to select points that are on this grid to build your geometry, and this can often help to position objects correctly.

1. Select the Draw Toolbox from the Sketching tab. 2. Click on Polyline and then create the shape shown below:

a. Click on the grid in the position where one of the points from the shape needs to be placed (it doesn't matter which point).

b. Then click on each successive point to make the shape. c. If at any point you click on the wrong place, just click with the right mouse button over the Model

View and select Back from the right mouse button menu to undo the point selection. d. To close the polyline after selecting the last point, click with the right mouse button to bring up a

menu and choose Closed End.


Geometry Creation

You will now create the main body of the mixer by revolving the new sketch around the Z-axis.

1. Select Revolve from the 3D Features Toolbar. This toolbar is located above the Model View. 2. Details of the Revolve operation are shown in the Details View at the bottom left of the window. Leave the

name of the Revolve as the default, Revolve1. 3. The Base Object is the name of the sketch to be revolved. It defaults to the sketch which you have just

created, Sketch1, so this setting does not need to be changed. 4. The Axis for the rotation does not have a default setting. In the Model View, click on the grid line which runs

along the Z-axis and then click on Apply in the Details View. You should find that the text next to Axis now changes to Selected. If instead it changes to Not Selected with a yellow background, click on the text Not Selected and then try selecting the axis again in the Model View, remembering to press Apply in the Details View after you have selected it.

5. Leave Operation as Add Material since you need to create a solid. (The other options allow you to modify existing solids and to deal with multiple solids.)

6. The sketch needs to be revolved by a full 360 degrees, so change Angle from 30 degrees to 360 degrees. Leave the other settings as default.

7. To activate the revolve operation, you need to click on Generate. This can be selected from the menu which appears when you click with the right mouse button almost anywhere in the window, or from the 3D Features Toolbar towards the top of the window.

After generation, you should find you have a solid as shown below.


Geometry Creation

Now you need to create the two side pipes. This involves creating and extruding two new sketches. To make it easier to see the grid when creating the sketches, the first step is to make the solid invisible for now.

1. In the Tree View, click on the plus sign next to 1 Part, 1 Body to open up the tree structure. 2. Position your cursor over the text Solid and then click with the right mouse button and select Hide Body. 3. Select ZXPlane in the Tree View again [XZPlane in ANSYS Workbench 8.0.1], and create a new sketch

based on this plane by using the New Sketch ( ) button on the Active Plane/Sketch Toolbar, which is located above the Model View.

4. Select the Sketching tab.5. Create a circle as shown in the picture below:

a. Select the Draw Toolbox.b. Select Circle, click on the grid at the center of the circle and then drag the mouse to define the

radius.

Now you need to extrude this sketch to make the first side-pipe.

1. Select Extrude from the 3D Features Toolbar. This toolbar is located above the Model View. 2. In the Details View at the bottom left of the window, change Direction to Reversed, in order to extrude in

the opposite direction to the plane normal. [Select Direction to be Normal in ANSYS Workbench 8.0.1 since


Geometry Creation

the plane normal is in the opposite direction.] 3. Change the Depth to 3 m. The rest of the settings can be left as their default. The Add Material setting will

mean that material is added to the existing solid, rather than a new solid being created

4. To activate the extrude operation, you need to click on Generate as before.

In order to see the result of this, you will have to make the solid visible again:

1. In the Tree View, position your cursor over the text Solid and then click with the right mouse button and select Show Body.

2. Click the middle mouse button over the Model View and drag the mouse about with the button held down to rotate the model. Check that the Solid looks like the picture below when rotated into a viewing position so that the side-pipe is clearly visible.

3. In the Tree View, position your cursor over the text Solid and then click with the right mouse button and select Hide Body.

To create the other side pipe, the same operations are used.

1. Select ZXPlane in the Tree View again [XZPlane in ANSYS Workbench 8.0.1], and create a new sketch

based on this plane by using the New Sketch ( ) button on the Active Plane/Sketch Toolbar, which is located above the Model View.

2. Select the Sketching tab.3. Right-click over the Model View and select View>Isometric View to put the sketch back into a sensible

viewing position. Then right-click again and select Zoom to Fit to zoom into the sketch, if it appears too small.

4. From the Draw Toolbox, select Circle and then create the second circle shown in the picture below:


Geometry Creation

1. Select Extrude from the 3D Features Toolbar. 2. In the Details View, set Direction to Normal, in order to extrude in the same direction as the plane normal.

[Select Direction to be Reversed in ANSYS Workbench 8.0.1 since the plane normal is in the opposite direction.]

3. Change the Depth to 3 m.

4. To activate the extrude operation, you need to click on Generate as before. 5. In the Tree View, position your cursor over the text Solid and then click with the right mouse button and

select Show Body.

The geometry is now complete.

1. Select File>Save and accept the default filename.

From this point, you could go straight into meshing the geometry. However, the tutorial continues by modifying the geometry in order to illustrate how to set dimensions on geometry objects. This is essential when creating geometry features which have dimensions which are not simple fractions of the model units, and so cannot use the grid for positioning the points and lines in the sketches.

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Introduction to CFX-Mesh Home Geometry Modification


Geometry Modification


In this section, you will change the radius of the inlet pipes to 0.45 m from the initial 0.5 m, without using the grid to position the circle.

1. Select Sketch2 in the Tree View, noting which circle it contains, and choose the Sketching tab. 2. Click on Dimensions (in the Sketching tab) to open the Dimensions Toolbox. 3. Click on Radius and then select the circle which forms Sketch2 from the Model View. 4. Click somewhere in the Model View to choose where the label for this dimension will be placed (this does

not affect the model in any way, it is purely for display purposes). 5. If you now look in the Details View at the bottom left of the screen, you will now find a section headed

Dimensions, which contains the radius R1, set to 0.5 m. For now, change the radius to be 0.45 m .

6. Click on Generate to activate the change.

You will see that both of the side pipes now have a slightly reduced radius as required. The radius of both the pipes changed simultaneously as the property of AutoConstraints is turned on by default. This automatically detects dimensions which are equal and constrains them to be equal so that when one changes, the other does also. See the DesignModeler documentation for more details.

You have now explicitly defined the dimension (radius) of the inlet pipe radii and can easily change it again if needed, perhaps if you change the geometry or if you made a mistake when originally specifying the radius. Whenever you are asked in later tutorials to create a geometry object of a particular size, you can either set up the grid to enable precise positioning of the geometry, or create the geometry at approximately the right size and then use the Dimensions Toolbox to specify the dimension exactly.

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Contents•CopyrightTutorial 1: Static Mixer> Geometry Modification


1. Change the radius back to 0.5 m. Remember to click on Generate to activate the change. 2. Select File>Save to save the geometry file.

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Geometry Creation Home Mesh Generation

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Mesh Generation

Mesh Generation

In order to set up the mesh, you must first move out of DesignModeler and into CFX-Mesh.

1. At the top of the ANSYS Workbench window, you should be able to see two tabs: StaticMixer [Project] and StaticMixer [DesignModeler]. Click on StaticMixer [Project] to return to the Project Page.

2. In the left-hand column, near the top, you should now see an entry Generate CFX Mesh. Click on this. 3. CFX-Mesh will open up. At first glance it looks very similar to DesignModeler.

Overview of CFX-Mesh

CFX-Mesh is designed to have the same look and feel as DesignModeler. In particular, this means that you can use the same mouse controls to manipulate the model.

One important difference between DesignModeler and CFX-Mesh is connected to the order of the items in the Tree View. In DesignModeler the Tree View shows items in the order that they were created, and the order affects the final geometry. In CFX-Mesh the order of the items in the Tree View are not important and all items of the same type are grouped together, independent of when they were created.

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Contents•CopyrightTutorial 1: Static Mixer> Mesh Generation

Mesh Generation

You will be able to see that various items are already present in the Tree View in DesignModeler; these are the default items and contain default settings. Some of the symbols next to items in the Tree View have slightly different implications in CFX-Mesh than they did in DesignModeler. In CFX-Mesh, the meanings are as follows:

Symbol Meaning

Everything is valid.

This means that there is something invalid about the definition of the item or one of its sub-items (which will also be marked with the same symbol). Often this will be because no required selection has been made.

The item is suppressed (inactive).

The item is suppressed and will be invalid when it is unsuppressed.

This indicates that an item contains associated sub-items . Left-click on the symbol to expand the item and display its contents.

Left-click on the symbol to close the item so that its contents are not visible in the tree.

The generation of the surface and volume mesh is controlled by the various features that you can access in CFX-Mesh. The type of controls available depend on the mesher used. By default, you are using the Delaunay Surface Mesher for surface meshing and Advancing Front Volume Mesher for volume meshing.

In this first example, you will only set up the most basic features for controlling the mesh generation. Only the basic length scale of the mesh will be specified.

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Setting up the Regions

The first step is to define some regions on the geometry. Composite 2D Regions are created from the solid faces (primitive 2D Regions) of the geometry. They can be used in CFX-Pre to assign boundary conditions, such as inlets and outlets, to the problem. You do not need to create Composite 2D Regions at all in CFX-Mesh, but it is easier to name and group faces into Composite 2D Regions in CFX-Mesh than it is to select the corresponding mesh in CFX-Pre. This example uses an inlet boundary condition at the entrance to each of the two side pipes, an outlet boundary condition on the end of the funnel outlet and a wall boundary condition for the remaining surfaces.

Note

There is an important distinction between primitive 2D Regions and the underlying solid faces, which applies when the model has more than one solid. This is explained in the Mesh Generation section of the Heating Coil tutorial.


Mesh Generation

If you look at the Tree View, you can see that under Regions, one Composite 2D Region is defined already, called Default 2D Region. This region will always contain all of the faces of the model which you have not explicitly assigned to another Composite 2D Region.

Create the Composite 2D Region for the first inlet:

1. Right-click over Regions in the Tree View. 2. Select Insert>Composite 2D Region. 3. A new object, Composite 2D Region 1, is inserted under Regions in the Tree View. Change its name to in1:

if the name is still highlighted, then just type over the existing name. If the name is not still highlighted, then right-click over the name, select Rename and then type over the existing name.

4. In the Details View, click in the box next to Location. There will now be two buttons, Apply and Cancel, and this means that you are ready to select the face from the Model View.

5. In the Model View, click on the circular face at the end of the side pipe which is at the position with the lowest value of the Y-coordinate. This will turn green to show that it has been selected, as in the picture below. You can rotate the model to make it easier to select the appropriate face by holding down the middle mouse button and moving the mouse over the geometry.

6. Click on Apply in the Details View.

Now create the second inlet:

1. Right-click over Regions in the Tree View. 2. Select Insert>Composite 2D Region. 3. A new object, Composite 2D Region 1, is inserted under Regions in the Tree View. Change its name to in2. 4. In the Details View, click in the box next to Location. There will now be two buttons, Apply and Cancel,

and this means that you are ready to select the face from the Model View. 5. In the Model View, click on the circular face at the end of the side pipe which is at the position with the

highest value of the Y-coordinate. 6. Click on Apply in the Details View.

Finally, create the region for the outlet:

1. Right-click over Regions in the Tree View and select Insert>Composite 2D Region. Change its name to out.


Mesh Generation

2. In the Details View, click in the box next to Location. Then select the circular face at the bottom of the mixer vessel, with the lowest value of the Z-coordinate.


It is not necessary to create a fourth Composite 2D Region for the walls of the static mixer. This is because any remaining faces which are not explicitly assigned to a Composite 2D Region are automatically assigned to the 2D Region named Default 2D Region. You can use this region in CFX-Pre to define the location of your wall boundary condition.

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Setting up the Mesh

You will only set a single size for all of the elements, in this tutorial. The next tutorial will then improve upon this coarse mesh.

1. Click on Default Body Spacing in the Tree View, which is contained in Mesh>Spacing. 2. In the Details View, change Maximum Spacing to 0.3 m. This is a coarse length scale for this model, but is

reasonable for a first run to generate an approximate solution and to test that the model is working correctly. 3. Press Enter on the keyboard to set this value.

The remaining settings will be left as their default.

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Generating the Surface Mesh

You will now have a look at the surface mesh to see the effect of the chosen length scale.

1. Right-click over Preview in the Tree View, and select Insert>Preview Group. 2. You want to view the surface mesh on all of the faces of the mixer, so you need to select all the faces in the

model as follows:a. Click in the box next to Location.b. Left-click somewhere in the Model View above and to the left of the model.c. Whilst holding down the mouse button, drag the mouse over the model to form a box which

completely encloses the model. All the surfaces within the box are then selected.d. Click on Apply in the Details View. The text should change to read 9 2D Regions.

3. Now right-click over Preview Group 1 and select Generate This Surface Mesh.

During the generation of the surface mesh, the progress will be displayed using the slider bar which appears to the bottom left of the CFX-Mesh window.


Mesh Generation

1. You can modify the way that it is displayed by clicking on Preview in the Tree View and changing the options shown in the Details View. For example, by changing the Mesh Render Mode you can switch to display the mesh in Wire Mesh rather than with solid faces. Simply click on the name Preview Group 1 to redisplay the surface mesh using the new settings.

It is not necessary to create the surface mesh within CFX-Mesh, since if it has not been created explicitly it will be automatically generated when you create the volume mesh. However, in many of these tutorials, you will create the surface mesh first, to demonstrate the effect of various mesh settings. It is generally a good idea to check the surface mesh before creating the volume mesh, to ensure that any settings you have made have the desired effect.

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Generating the Volume Mesh

The volume mesh and all of the region information required for CFX-Pre is stored in a CFX-5 GTM (Geometry, Topology and Mesh) File. The GTM File is read into CFX-Pre at the start of the simulation definition. Before you generate the volume mesh, you must ensure that the GTM File name is set to an appropriate location.

1. Click on Options in the Tree View, which is contained in Mesh. 2. Change GTM Filename to StaticMixerMesh.gtm. To do this, click on the filename shown and then

click on the button with the three dots. Type the new name into the file browser which appears.

Now generate the volume mesh.

1. Right-click on Mesh in the Tree View and select Generate Volume Mesh.

During the generation of the volume mesh, the progress will be displayed using the slider bar which appears to the bottom left of the CFX-Mesh window. When the volume mesh is complete, the slider bar will disappear and you will be able to take control of the user interface again.

The mesh is now complete.


Mesh Generation

1. Select File>Save to save the CFX-Mesh database as StaticMixer.cmdb in the same directory as the other project files.

2. At the top of the ANSYS Workbench window, you should be able to see three tabs: StaticMixer [Project], StaticMixer [DesignModeler] and StaticMixer [CFX-Mesh]. Click on StaticMixer [Project] to return to the Project Page.

3. Select File>Save to save the project. 4. Exit from ANSYS Workbench by selecting File>Exit.

You can now work through the CFX-5.7 example “Tutorial 1: Flow in a Static Mixer” using the newly-generated mesh.

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Geometry Modification Home Tutorial 2: Static Mixer (Refined Mesh)


Tutorial 2: Static Mixer (Refined Mesh)


This example modifies the mesh for the static mixer geometry created in the previous example, and assumes that you have access to the files created as part of that example. The following geometry and meshing features are illustrated:

● modifying an existing mesh setup; and ● Inflation.

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Mesh Generation Home Modifying the Mesh Generation

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Modifying the Mesh Generation


Opening the Existing Project

1. Open ANSYS Workbench. 2. In ANSYS Workbench 8.0.1 only, select Open an Existing Project from the left side of the window. 3. In the main part of the window, click on the existing StaticMixer project, and click on Open. If it does not

appear in the list of recent projects (perhaps because you moved the files), then use Browse to locate the project file StaticMixer.wbdb instead.

4. To open CFX-Mesh, double-click on StaticMixer.

CFX-Mesh will now be opened with the geometry and mesh settings from the previous tutorial.

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Modifying the Mesh Settings

The first step is to create a refined mesh size over the whole geometry.

1. Click on Default Body Spacing in the Tree View, which is contained in Mesh>Spacing. 2. In the Details View, change Maximum Spacing to 0.2 m. This is a smaller length scale for the model than

set previously (0.3 m). 3. Press Enter on the keyboard to set this value.

The next step is to create an Inflated Boundary on the walls of the mixer. Creating inflated boundaries generates prismatic elements from the surface by inflating triangular elements into the solid. As a result, near the wall boundaries there will be layers of flat prismatic (wedge-shaped) elements which provide a smaller mesh length scale in the direction perpendicular to the wall. This provides better resolution of the velocity field near the wall, where it changes rapidly.

Inflation can greatly improve accuracy, particularly in a model with a high aspect ratio, such as a long narrow pipe, or in a model where turbulence is significant. Inflation should always be used when you are interested in lift, drag or pressure drop in the model.

Away from the wall boundaries, the mesh elements will be tetrahedral as they were in Tutorial 1.

First, you will set the parameters used to control the inflation process, and then you will create the Inflated Boundary

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Contents•CopyrightTutorial 2: Static Mixer (Refined Mesh)> Modifying the Mesh Generation


itself.

1. Click on Inflation in the Tree View. 2. In the Details View, set Number of Inflated Layers to 5. This will give five layers of prism elements. 3. Set Expansion Factor to 1.3. This controls how fast the thickness of the prism elements grows in successive

layers away from the wall. 4. Leave the other settings as their default values. 5. In the Tree View, right-click on Inflation and select Insert>Inflated Boundary. 6. In the Details View, click in the box next to Location, and then click on Default 2D Region in the Tree

View to select the faces which are in the Default 2D Region for the Inflated Boundary. Click on Apply in the Details View. The text should change to read 1 Composite.

7. Set Maximum Thickness to 0.2 m.

This creates an Inflated Boundary that uses all the faces in the Default 2D Region. If you later change the 2D Region settings so that the Default 2D Region contains different faces, the Inflated Boundary will automatically update to always use the faces in the Default 2D Region at the time when the mesh is generated.

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Finally, you can generate the volume mesh.

1. Click on Options in the Tree View, and change GTM Filename to StaticMixerRefMesh.gtm. 2. Right-click on Mesh in the Tree View and select Generate Volume Mesh.


1. Select File>Save to save the CFX-Mesh database. 2. Exit from ANSYS Workbench by selecting File>Exit.

You can now work through the CFX-5.7 example “Tutorial 2: Flow in a Static Mixer (Refined Mesh)” using the newly-generated mesh.

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Home Tutorial 3: Process Injection Mixing Pipe

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Tutorial 3: Process Injection Mixing Pipe


This example shows how to create a simple pipe junction, using Sweep to create the pipe profile. The following geometry and meshing features are illustrated:

● Face Spacing, for refining the mesh on a particular face; ● Inflation; and ● full surface mesh generation, to preview the full surface mesh.

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Modifying the Mesh Generation Home Geometry Creation

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Geometry Creation

Geometry Creation


1. Open ANSYS Workbench, create a new project, and save it as InjectMixer. If you need to, refer to the instructions in the Geometry Creation section of the Static Mixer tutorial for more details on how to do this.

2. Open up DesignModeler, specifying the units as meters.

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Creating the Main Pipe

To create the main pipe, you will use the Sweep operation. Sweep requires the use of two sketches: one defines the profile to be swept (in this case, a circle) and the other defines the path through which the profile is swept. The profile will be created first.

1. Create a new plane as follows. Select the XYPlane in the Tree View and then click on the New Plane icon (

) from the Active Plane/Sketch Toolbar, near the top of the ANSYS Workbench window. Clicking on XYPlane first ensures that the new plane is based on the XYPlane.

2. In the Details View, set Transform 1 (RMB) to Offset Z, and set the Value of the offset to -4 m.

3. Click on Generate to create the plane. 4. Create a new sketch as follows. Select Plane4 in the Tree View and then click on the New Sketch icon (

) from the Active Plane/Sketch Toolbar, near the top of the ANSYS Workbench window. Clicking on the plane first ensures that the new sketch is based on Plane4.

5. Use Grid from the Settings Toolbox of the Sketching tab to set Show in 2D and Snap to ON. 6. Set Major Grid Spacing to 1.0 m and Minor-Steps per Major to 2. 7. Use Circle from the Draw Toolbox of the Sketching tab to draw a circle of radius 0.5 m, centered on X = 0

m, Y = -2 m. The grid settings you have just set up will help you to position the circle and set its radius correctly.

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Contents•CopyrightTutorial 3: Process Injection Mixing Pipe> Geometry Creation

Geometry Creation

Now create the path:

1. Create a new sketch ( ) based on the YZPlane: as before, make the YZPlane active first by clicking on it, and then use the New Sketch icon to create the sketch based upon it.

2. Use Grid from the Settings Toolbox of the Sketching tab to set Show in 2D and Snap to ON. 3. Set Major Grid Spacing to 1.0 m and Minor-Steps per Major to 2. 4. Use Line from the Draw Toolbox of the Sketching tab to draw two straight lines on the sketch, as shown in

the picture below. 5. Click on Arc by Center from the Draw Toolbox, and click once on the origin (center of the Arc shown in the

picture below). Now select one of the end points of the arc, and then move the mouse round to the other end point and click on it to draw the quarter-circle. If the wrong part of the arc is drawn (i.e. a 270 degree segment instead of a 90 segment) then click on Undo (from the Undo/Redo Toolbar at the top of the ANSYS Workbench window) and try again, making sure that after you click on the first end point, you move the mouse in the correct direction for the arc that is to be drawn.

Now make the pipe itself.

1. Select Sweep from the 3D Features Toolbar. 2. Set the Profile to be Sketch1: click on Sketch1 in the Tree View and then click on Apply in the Details

View at the bottom-left of the screen. 3. Set the Path to Sketch2: click on the Not selected text next to Path, click on Sketch2 in the Tree View, and

then click on Apply.


Geometry Creation

4. Click on Generate to create the pipe.

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Creating the Side Pipe

1. Create a new plane ( ), based on the ZXPlane: as before, make the ZXPlane active first by clicking on it, and then use the New Plane icon to create the plane based upon it. [If you are using ANSYS Workbench 8.0.1 then use the XZPlane; the plane normal is then reversed.]

2. In the Details View, set Transform 1 to Offset Global Z, and set the Value of the offset to 2 m. 3. Set Additional Transform? to Yes, and then set Transform 2 to Offset Global Y. Set the Value of the

offset to -3 m.

4. Click on Generate to create the plane.

5. Create a new sketch ( ) based on the new plane. 6. Use Circle from the Draw Toolbox of the Sketching tab to create the circle centered on the origin with a

radius of 0.15 m. Create the circle initially with any convenient radius, and then use Radius from the Dimensions Toolbox of the Sketching tab to specify the radius more precisely, as described in the Geometry Modification section of the Static Mixer tutorial.

7. Select Extrude from the 3D Features Toolbar. 8. Set Base Object to be the new sketch (Sketch3), and set Operation to Add Material. 9. Set Direction to Normal [Reversed in ANSYS Workbench 8.0.1] and Type to Fixed. Set Depth to 3 m.

10. Click on Generate to create the side-pipe.

Note that the extrusion of Sketch3 has to reach the main pipe body, but that it does not matter if it extends into the body. It is possible to extrude To Next, which means that the extrusion will stop when it meets another geometry object, but the net effect would be no different than using the Fixed extent.


1. Select File>Save to save the geometry file.


Geometry Creation

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Home Mesh Generation


Mesh Generation

Mesh Generation

First open CFX-Mesh.

1. Switch from the DesignModeler to the Project Page using the tabs at the top of the window.

2. Click on the name of the DesignModeler entry, InjectMixer, and then Generate CFX Mesh to the left of the Project Page.


As before, you need to set up some 2D Regions.

Create the region for the side inlet:

1. Right-click over Regions in the Tree View and select Insert>Composite 2D Region. Change its name to side inlet.

2. In the Details View, click in the box next to Location. Then select the circular face at the end of the small side pipe.


Create the region for the main inlet:

1. Create a Composite 2D Region called main inlet. 2. In the Details View, click in the box next to Location. Then select the circular face at the end of the main

pipe, with the lowest Z-coordinate. 3. Click on Apply in the Details View.

Create the region for the outlet:

1. Create a Composite 2D Region called outlet. 2. In the Details View, click in the box next to Location. Then select the circular face at the other end of the

main pipe, with the highest Y-coordinate. Click on Apply in the Details View.

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Setting up the Mesh

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Contents•CopyrightTutorial 3: Process Injection Mixing Pipe> Mesh Generation

Mesh Generation

Set the Maximum Spacing:

1. Click on Default Body Spacing in the Tree View, which is contained in Mesh>Spacing. 2. In the Details View, change Maximum Spacing to 0.25 m, and press Enter on the keyboard to set this value.

It is desirable to have a reasonably fine mesh in the region of the side pipe, since the features of the flow in this region are likely to be smaller than the Maximum Spacing that you just set. To do this, you will set a Face Spacing to concentrate nodes and elements in this region. You can specify how quickly the mesh elements grow as you move away from the selected face using an expansion factor.

Face Spacings act like sources, determining the size and distribution of elements in the region around that face. They affect both the triangular surface mesh and the volume mesh. It is also possible to create Controls, which have a similar effect but are applied to points, lines or triangles instead of faces.

In this tutorial, you will define a Face Spacing on the exterior of the side pipe to control the size of the elements generated in the vicinity.

1. Right-click on Spacing and select Insert>Face Spacing 2. In the Details View, set Face Spacing Type to Constant, and set the Constant Edge Length to 0.1 m. This

sets the mesh length scale for the Face Spacing. 3. Set the Radius of Influence to 0.0 m. The mesh control is applied only to the surface and not to a volume

surrounding the surface. 4. Set the Expansion Factor to 1.2. This specifies how quickly the mesh elements grow as you move away

from the face. As you move away, each element will be approximately 1.2 times as big as the previous one in the region in which the expansion takes place, until the mesh length scale reaches the Maximum Spacing of 0.25 m which was set in the last section.

5. Click in the box next to Location. Then select the cylindrical face of the side pipe. Click on Apply in the Details View.

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You will now have a look at the surface mesh to see the effect of the chosen length scale.

1. Right-click over Preview in the Tree View, and select Insert>Preview Group. 2. You want to view the surface mesh on all of the faces of the mixer, so you need to select all the faces in the

model as follows:a. Click in the box next to Location.b. Left-click somewhere in the Model View above and to the left of the model.c. Whilst holding down the mouse button, drag the mouse over the model to form a box which

completely encloses the model. All the surfaces within the box are then selected.d. Click on Apply in the Details View. The text should change to read 7 2D Regions.

3. Now right-click over Preview Group 1 and select Generate This Surface Mesh. 4. When the surface mesh is complete, click on Preview Group 1 in the Tree View to display it.


Mesh Generation

You should be able to see that the mesh is finer around the side pipe than it is elsewhere in the geometry.

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Setting up Inflation

The velocity gradients near the pipe wall surfaces can vary significantly, so it is advisable to apply inflation in these areas.

1. Click on Inflation in the Tree View. 2. In the Details View, set Number of Inflated Layers to 5. 3. Leave the other settings as their default values. 4. In the Tree View, right-click on Inflation and select Insert>Inflated Boundary. 5. In the Details View, click in the box next to Location, and then click on Default 2D Region in the Tree

View to select the faces which are in the Default 2D Region for the Inflated Boundary. 6. Leave Maximum Thickness as the default setting.

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1. Click on Options in the Tree View, and change GTM Filename to InjectMixerMesh.gtm. 2. Right-click on Mesh in the Tree View and select Generate Volume Mesh.


Mesh Generation


1. Select File>Save to save the CFX-Mesh database. 2. Switch to the Project Page using the tabs at the top of the window, and choose File>Save to save the project. 3. Exit from ANSYS Workbench by selecting File>Exit.

You can now work through the CFX-5.7 example “Tutorial 3: Flow in a Process Injection Mixing Pipe” using the newly-generated mesh.

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Geometry Creation Home Tutorial 4: Circular Vent


Tutorial 4: Circular Vent


This example creates the geometry and mesh for a simple chimney stack. The following geometry and meshing features are illustrated:

● Controls, for refining the mesh along a line; ● Inflation; and ● Preview Groups, for previewing part of the surface mesh.

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Mesh Generation Home Geometry Creation

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Geometry Creation

Geometry Creation


1. Open ANSYS Workbench, and create a new project. 2. Open up DesignModeler, specifying the units as meters.

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Creating the Solid

The geometry consists of a cylindrical pipe which is placed in the center of a cylindrical region.

1. Create a new sketch ( ) based on the XYPlane. 2. Use Circle from the Draw Toolbox of the Sketching tab to draw a circle in the new sketch, centered on the

origin and with radius 10 m.

If you just extruded this circle, you would get a cylinder which consisted of three faces: circular top, circular bottom and the curved cylindrical face. However, you will need to apply a boundary condition in the CFD simulation to just half of the curved cylindrical face. The only way to do that effectively is to create the cylindrical face in two parts. This means that you need to modify the circle before extruding.

1. Select Construction Point at Intersection from the Draw Toolbox. This is located right at the bottom of the list.

2. Select the Y-axis and then select the circle somewhere near where it intersects the Y-axis. You should find that a point appears at the intersection.

3. Now select the Y-axis again, and select the circle somewhere near where the other intersection of it and the Y-axis occurs. A second construction point should appear.

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Contents•CopyrightTutorial 4: Circular Vent> Geometry Creation

Geometry Creation

4. Select Split from the Modify Toolbox of the Sketching tab. Right-click over the Model View and select Split Edge at All Points.

5. Click on the circle to perform the split.

6. Select Extrude from the 3D Features Toolbar. 7. Set Base Object to be the new sketch (Sketch1), and set Operation as Add Material. Set Depth to be 10 m. 8. Set Merge Topology? to No. This stops DesignModeler from optimizing the surfaces created by combining

them where possible, which would prevent the splits in the circle from having any effect.

9. Click on Generate to create the cylinder.

Now you will cut material from this cylinder to form the vent itself.

1. Create another new sketch ( ) based on the XYPlane. 2. Use Circle from the Draw Toolbox of the Sketching tab to draw a circle in the new sketch, centered on the

origin and with radius 1 m.

3. Select Extrude from the 3D Features Toolbar. 4. Set Base Object to be the new sketch (Sketch2), and set Operation as Cut Material.

5. Set Depth to be 5 m, and click on Generate to cut the pipe out of the large cylindrical region.



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Tutorial 4: Circular Vent Home Mesh Generation

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Mesh Generation

Mesh Generation


1. Switch from the DesignModeler to the Project Page using the tabs at the top of the window and open CFX-Mesh.


Create the region for the wind inlet:

1. Create a Composite 2D Region called Wind. 2. In the Details View, click in the box next to Location. Then select the large curved face with the lowest X-

coordinates. Click on Apply in the Details View.

Create the region for the opening to the atmosphere:

1. Create a Composite 2D Region called Atmosphere. 2. Select the other large curved face and the top of the large cylinder (highest Z-coordinate) to apply it to.

Create the region for the vent opening to the atmosphere:

1. Create a Composite 2D Region called Vent. 2. Select the small circular face at the top of the vent to apply it to. This can be slightly tricky to select directly

since from most viewing positions it is behind another face. Either: ● Click over the axes in the bottom right corner of the Model View in the position shown in the picture

below. As you move the cursor into this position, the black “-Z”-axis will appear (it is not shown by default). This will put the geometry into a good position for picking the required face.

● This viewing position allows you to view the bottom of the geometry and you can look up the vent itself to see the small circular face at the top of the vent without it being behind another face. So you can now select it directly.

or

● Click over the required face even though it is behind another face. The face at the front will be

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Contents•CopyrightTutorial 4: Circular Vent> Mesh Generation

Mesh Generation

selected and a stack of Selection Rectangles (shown below) will appear at the bottom left of the Model View. Note that exactly how many selection rectangles there are will depend on exactly what the viewing position of your model was when you clicked over the face.

● Each rectangle represents a face which was under the cursor when you clicked, with the left-most rectangle representing the front face. You will be able to see from the selection rectangles that this front face is outlined in red, which means that it is currently selected. Click on this selection rectangle whilst holding down the Ctrl key in order to deselect it.

● Now select the rectangle which represents the face which you want. As you click on the rectangle, the corresponding face in the geometry will highlight. You may need to experiment to get the correct face.

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Setting up the Mesh



Create inflated surfaces for the vent and ground surfaces:

1. Click on Inflation in the Tree View. 2. In the Details View, set Number of Inflated Layers to 4. 3. Leave the other settings as their default values. 4. In the Tree View, right-click on Inflation and select Insert>Inflated Boundary. 5. Select the faces for the boundary. The two surfaces which it should be applied to are the side of the vent and

the bottom of the large cylinder (lowest Z-coordinate). 6. Set Maximum Thickness to 0.2 m.

Create a Control in the center of the vent to refine the mesh in this region of the simulation. You will use a Line Control, which refines the mesh in the region around a line.

Point, Line and Triangle Controls all make use of the Point Spacing object. This defines a set of spacing values, which can be applied to the various Controls as desired.

1. Right-click on Controls in the Tree View, and select Insert>Point Spacing. 2. In the Details View, set Length Scale to 0.33 m. Set Radius of Influence to 1.0 m, and Expansion Factor

to 1.15 m. 3. Right-click on Controls in the Tree View, and select Insert>Line Control. 4. In the Details View, click in the box next to the first Point. There will now be two buttons, Apply and


Mesh Generation

Cancel. Click on Apply without selecting anything in the Model View, and a box will appear to allow you to enter coordinate values. Set the coordinates of Point 1 to be [0 0 0].

5. Set the coordinates of Point 2 to be [0 0 4], in the same way. 6. You want the specified Point Spacing to apply to both points, so leave Spacing Definitions set to Uniform. 7. Click in the box next to Spacing, and then click on Point Spacing 1 in the Tree View to select the

appropriate Point Spacing for the Control. 8. In order to better see the inside of the vent, click on Geometry in the Tree View, and in the Details View, set

Transparency to 40 %.

If you ensure that the new Line Control is selected in the Tree View, and look at the vent in the Model View, you should be able to see where the Control has been created, as shown below. The line itself should be clearly visible, and the two spheres at each end show the Radius of Influence.

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To get a clear view of how the Control affects the mesh, it is convenient to generate just part of the surface mesh.

1. Right-click over Preview in the Tree View, and select Insert>Preview Group. 2. Change the name of the Preview Group to Ground. 3. For Location, select the large circular face (with a hole in) at the bottom of the geometry (lowest Z-

coordinate). 4. Now right-click over the Preview Group Ground in the Tree View, and select Generate This Surface

Mesh. The surface mesh will be generated on just the corresponding face.


Mesh Generation

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1. Click on Options in the Tree View, and change GTM Filename to CircVentMesh.gtm. 2. Right-click on Mesh in the Tree View and select Generate Volume Mesh.



You can now work through the CFX-5.7 example “Tutorial 4: Flow from a Circular Vent” using the newly-generated mesh.

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Geometry Creation Home Tutorial 5: Blunt Body


Tutorial 5: Blunt Body


This example creates the geometry and mesh for a simulation of flow over a vehicle body shape. Due to the symmetry of both the geometry and the flow pattern, only half of the body needs to be modeled. The following geometry and meshing features are illustrated:

● Face Spacing, for refining the mesh on a particular face; ● Inflation; ● Proximity, for refining the volume mesh where two faces are close together; and ● Preview Groups, for previewing part of the surface mesh.

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Geometry Creation

Geometry Creation



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Creating the Body

To create the body shape, you will create a sketch and then extrude it. A Cut Material operation will then be used to shape the rounded end of the body.

1. Create a new sketch ( ) based on the ZXPlane. [If you are using ANSYS Workbench 8.0.1 then use the XZPlane; the plane normal is then reversed.]

2. Use Rectangle from the Draw Toolbox of the Sketching tab to draw a rectangle as shown below (note the orientation of the axes). The required dimensions are: H1 = 1.44 m, V2 = 5.22 m. [If you are using ANSYS Workbench 8.0.1 then you will find that you have to apply a Vertical dimension for the length labeled “H1” and a Horizontal dimension for the length labeled “V2”.]

3. Select Fillet from the Modify Toolbox of the Sketching tab, and enter 0.5 m for the Radius in the box which opens to the right of the word Fillet.

4. Select the two corners of the geometry that are on the Z-axis, to create the two fillets, as shown below.

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Contents•CopyrightTutorial 5: Blunt Body> Geometry Creation

Geometry Creation

5. Select Chamfer from the Modify Toolbox, and enter 1.11 m for the Length in the box which opens to the right of the word Chamfer.

6. Select the top right corner of the geometry to create the chamfer, as shown below.

7. Use Angle from the Dimensions Toolbox to specify the angle between the chamfer and the top of the sketch to be 25 degrees, as shown below. If the wrong angle is displayed just after you click on the second edge, then (before you click to position the dimension) right-click and choose Alternate Angle until the correct angle is displayed. After you have selected both of the edges which form the angle, remember to click once to position the label before typing the angle, 25 degrees, into the Dimensions box in the Details View.

8. Use Length from the Dimensions Toolbox to specify the length of the slanted edge to be 1.11 m, as shown below.


Geometry Creation

The sketch is now complete, and can be extruded to form the body.

1. Select Extrude from the 3D Features Toolbar. 2. Set Base Object to be the new sketch (Sketch1), and set Operation as Add Material. Set Direction to

Reversed. [Select Direction to be Normal in ANSYS Workbench 8.0.1 since the plane normal is in the opposite direction.]

3. Set Depth to be 0.9725 m, and click on Generate to create the solid.

The front end of the blunt body is already rounded; however, some more material needs to be cut away from it to get the correct shape.

1. Create a new sketch ( ) based on the XYPlane. 2. You need to create the sketch shown in the picture below. One way to do this is as follows:

a. Use Polyline from the Draw Toolbox of the Sketching tab to draw the two straight lines of approximately the right length. After you have clicked to place the third point (at the end of the second line), then right-click and select Open End to finish the polyline.

b. Select Equal Length from the Constraints Toolbox and then click on the two straight lines. This ensures that they will always remain the same length, so if one changes, the other one will also change.

c. Use Arc by Tangent from the Draw Toolbox to draw the quarter-circle, select the two end points of the polyline. If the wrong part of the arc is being drawn (i.e. a 270 degree segment instead of a 90 segment) just before you click on the second end point, then right-click and select Reverse to correct it.

d. Use Vertical and Radius from the Dimensions Toolbox to fix the two dimensions shown. The values required are: V1 = 0.9725 m, R2 = 0.5 m.

3. Select Extrude from the 3D Features Toolbar. 4. Set Base Object to be the new sketch (Sketch2), and set Operation as Cut Material.

5. Set Depth to be 1.5 m, and click on Generate to cut away the material.

The end of your blunt body should now look the same as in the picture below.


Geometry Creation

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Creating the Containing Box

The next step is to create the box around the blunt body to form the region for the fluid flow simulation. To stop the new solid from merging with the blunt body, first you must freeze it, and you will also give it a name to identify it more easily later on.

1. In the Tree View, click on the plus sign next to “1 Part, 1 Body” and then select Solid from the tree underneath this entry. In the Details View, you will now see the information relating to the body. Click on the word “Solid” in this information, and change it to read “Blunt Body”. Pressing Enter on the keyboard will let the name change take effect.

2. Select Tools>Freeze from the Menu Toolbar to freeze the body.

3. Create a new sketch ( ) based on the ZXPlane [XZPlane in ANSYS Workbench 8.0.1]. 4. Use Rectangle from the Draw Toolbox of the Sketching tab to draw a rectangle as shown below. Note that

the rectangle extends below the bottom of the body (below the XYPlane). The required dimensions are: V5 = 12.39 m, V6 = 17.61 m, H7 = 4.75 m, H8 = 0.25 m. [If you are using ANSYS Workbench 8.0.1 then you will find that you have to apply a Vertical dimension for the lengths labeled “H7” and “H8” and a Horizontal dimension for the lengths labeled “V5” and “V6”.]

5. Select Extrude from the 3D Features Toolbar. 6. Set Base Object to be the new sketch (Sketch3), and set Operation as Add Material. 7. Set Direction to Reversed [Normal in ANSYS Workbench 8.0.1] and Type to Fixed. Set Depth to be 5.15

m, and click on Generate to create the solid.


Geometry Creation

You can now cut out the blunt body from the containing box, to leave just the region of interest for the CFD simulation.

1. Select Create>Body Operation from the Menu Toolbar. 2. Set Type to Cut Material and Bodies to the blunt body. To select the blunt body, you can click on Blunt

Body in the Tree View, under “2 Parts, 2 Bodies”.

3. Click on Generate to remove the blunt body from its containing box.



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Tutorial 5: Blunt Body Home Mesh Generation


Mesh Generation

Mesh Generation




Create the region for the inlet:

1. Create a Composite 2D Region called Inlet. 2. Select the rectangular face of the solid with the lowest X-coordinate to apply it to.

Create the region for the outlet:

1. Create a Composite 2D Region called Outlet. 2. Select the rectangular face of the solid with the highest X-coordinate to apply it to.

Create the region for the top free-slip wall:

1. Create a Composite 2D Region called Free1. 2. Select the rectangular face of the solid with the highest Z-coordinate to apply it to.

Create the region for the side free-slip wall:

1. Create a Composite 2D Region called Free2. 2. Select the rectangular face of the solid with the lowest Y-coordinate to apply it to.

Create the region for the symmetry plane:

1. Create a Composite 2D Region called SymP. 2. Select the rectangular face of the solid with the highest Y-coordinate to apply it to.

It is a good idea to create a separate region on the surface of the blunt body for visualization purposes and for setting mesh controls.

1. Create a Composite 2D Region called Body.

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Contents•CopyrightTutorial 5: Blunt Body> Mesh Generation

Mesh Generation

2. You need to select the nine faces of the blunt body to apply this to. This can be done using Box Select: whilst holding down the left mouse button, drag a box across the body surfaces (as shown in the picture below) to select them. All the surfaces which are fully enclosed in this box will be selected. Press Apply in the Details View to accept the selection.

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Setting up the Mesh



It is desirable to have a reasonably fine mesh around the surfaces of the blunt body. You can create a Face Spacing to concentrate nodes and elements in this region.

1. Right-click on Spacing and select Insert>Face Spacing 2. In the Details View, set Face Spacing Type to Constant, and set the Constant Edge Length to 0.15 m. This

sets the mesh length scale for the Face Spacing. 3. Set the Radius of Influence to 0.0 m, and Expansion Factor to 1.2. 4. Click in the box next to Location. Then select the Body Composite 2D Region by clicking on its name in the

Tree View. Click on Apply in the Details View.

You can use Inflation to produce a thin layer of prismatic elements around the body external surface and along the ground.

1. Click on Inflation in the Tree View. In the Details View, set Number of Inflated Layers to 5. 2. Set Expansion Factor to 1.3. 3. In the Tree View, right-click on Inflation and select Insert>Inflated Boundary. 4. For Location, select both Body and Default 2D Region from the Tree View. Hold down the Ctrl key in

order to select the second of these.


Mesh Generation


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Obtain a view of the surface mesh over the surface of the blunt body using a Preview Group:

1. Right-click over Preview in the Tree View, and select Insert>Preview Group. Change the name of the Preview Group to Body.

2. For Location, select the Composite 2D Region Body from the Tree View. 3. Now right-click over the Preview Group Body in the Tree View, and select Generate This Surface Mesh.

The surface mesh will be generated on just the corresponding faces.

Next, take a look at the mesh on the symmetry plane:

1. Right-click over Preview in the Tree View, and select Insert>Preview Group. Change the name of the Preview Group to SymP.

2. For Location, select the Composite 2D Region SymP from the Tree View. 3. Now right-click over the Preview Group SymP in the Tree View, and select Generate This Surface Mesh.

The surface mesh will be generated on just the corresponding faces. 4. Click on the green Y-axis in the triad at the bottom right of the Model View to put the geometry into a good

viewing position to inspect this mesh, and click on the Preview Group in the Tree View to display it.

If you look at the mesh between the body and the ground, you will see that it is of poor quality: the elements are


Mesh Generation

distorted due to the small gap between the body and the ground. To avoid this, you can use Surface Proximity. Surface Proximity is a meshing feature that detects close surfaces, such as the base of the body and the ground, and then refines the mesh so that a minimum number of mesh elements span the gap. The default number of elements across the gap is 4, and this is the minimum recommended when both faces have inflation, such as in this case.

You can turn on Surface Proximity as follows:

1. Click on Proximity in the Tree View. 2. Set Surface Proximity to Yes and change the Number of Elements Across Gap to 3.

The value of 3 is lower than is generally recommended, in order to keep the mesh small for the tutorial.

1. Regenerate the mesh on the Preview Group SymP by right-clicking on its name in the Tree View and selecting Generate This Surface Mesh.

You will now see that 3 elements now span the gap. The surface mesher has detected the close proximity of the two surfaces and refined the mesh in this region, leading to elements of a higher quality. The effect of turning Proximity on has also led to a smoother transition between the element sizes as you move away from the body.

Surface Proximity is an automatic method that produces higher quality meshes for many geometries. However, you should always check the size of the mesh produced, as it can dramatically increase the number of nodes. In some cases it is important to use a minimum edge length to prevent over-refinement of the mesh; see the CFX-Mesh Help under Surface Proximity for more details.

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Mesh Generation



1. Click on Options in the Tree View, and change GTM Filename to BluntBodyMesh.gtm. 2. Right-click on Mesh in the Tree View and select Generate Volume Mesh.



You can now work through the CFX-5.7 example “Tutorial 5: Flow Around a Blunt Body” using the newly-generated mesh.

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Geometry Creation Home Tutorial 6: Butterfly Valve


Tutorial 6: Butterfly Valve


This example creates the geometry and mesh for a butterfly valve in a pipe. The following geometry and meshing features are illustrated:

● Parasolid import of the valve geometry; ● splitting the geometry along a line; ● curvature-sensitive meshing; ● Face Spacing, for refining the mesh on a particular face; ● Inflation; ● Proximity, for refining the volume mesh when two faces are close together; and ● Preview Groups, for previewing part of the surface mesh.

This tutorial requires you to have a copy of the Parasolid file PipeValve.x_t. If you do not already have this file, then download it here (you will need to execute the downloaded file to extract the Parasolid file).

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http://www.ansys.com/dm_how_tos/cm_pipevalve.exe

Geometry Creation

Geometry Creation


1. Open ANSYS Workbench, and create a new project. 2. Open up DesignModeler, specifying the units as millimeters. 3. Specify the units as millimeters, and open up DesignModeler.

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Setting up the Valve Geometry

The first step is to import the valve geometry.

1. Select File>Import External Geometry File... from the Menu Toolbar. 2. In the file browser which opens, locate the file PipeValve.x_t and choose to Open it. (If you have not

already got this file, refer to the introduction to this tutorial for details of where to find it.)

3. Click on Generate to import the valve.

The valve is imported with its flat faces parallel to the ZXPlane. For the simulation, it needs to be tilted at an angle of 35 degrees, so the next step is to move it. In DesignModeler, the way to move a body is to move it from one plane to another. So first you need to create the new plane, and then use a Body Operation to transform the valve.

1. Create a new plane ( ), based on the ZXPlane. [In ANSYS Workbench 8.0.1, create the new plane based on the XZPlane.]

2. In the Details View, set Transform 1 to Rotate about Global X, and set the Value of the rotation to -35 degrees.

3. Click on Generate to create the plane. 4. Select Create>Body Operation from the Menu Toolbar. 5. Set Type as Move and select the valve as Bodies. To select the valve, you can click on it in the Model View. 6. Set Source Plane to ZXPlane and Destination Plane to Plane4. [In ANSYS Workbench 8.0.1, set Source

Plane to the XZPlane.].

7. Click on Generate to move the valve. 8. Click on ZXPlane to show the original plane, so that you can see how the valve has moved. [In ANSYS

Workbench 8.0.1, click on the XZPlane, and note that the normal will be in the opposite direction to the one shown in the picture below.].

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Contents•CopyrightTutorial 6: Butterfly Valve> Geometry Creation

Geometry Creation

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Creating the Pipe

You now need to create the pipe which surrounds the valve, in which the fluid flows. To stop the new solid from merging with the valve, first you must freeze the valve solid, and you will also give it a name to identify it more easily later on.

1. In the Tree View, click on the plus sign next to “1 Part, 1 Body” and then select Solid from the tree underneath this entry. In the Details View, you will now see the information relating to the body. Click on the word “Solid” in this information, and change it to read “Valve”. Pressing Enter on the keyboard will let the name change take effect.

2. Select Tools>Freeze from the Menu Toolbar to freeze the valve.

3. Create a new plane ( ), based on the XYPlane. 4. In the Details View, set Transform 1 to Offset Z, and set the Value of the offset to -100 mm.

5. Click on Generate to create the plane. You may need to zoom out from the valve geometry to see the new plane.

6. Create a new sketch ( ) based on the new plane, Plane5. 7. Use Circle from the Draw Toolbox of the Sketching tab to draw a circle in the new sketch, centered on the

origin and with radius 20 mm.

8. Select Extrude from the 3D Features Toolbar. 9. Set Base Object to be the new sketch (Sketch1), and set Operation as Add Material.

10. Set Depth to be 200 mm, and click on Generate to create the pipe.

Now you can subtract the solid material in the valve from the pipe, to leave a valve-shaped hole in the pipe. The remaining solid is exactly the volume in which fluid flows, ready to set up a simulation of fluid flow past the valve.

1. Select Create>Body Operation from the Menu Toolbar. 2. Set Type to Cut Material and Bodies to the valve. To select the valve, you can click on Valve in the Tree


Geometry Creation

View, under “2 Parts, 2 Bodies”.

3. Click on Generate to remove the valve material from the pipe.

Although it is not easy to see, the pipe now has a valve-shaped hole in it.

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Splitting the Solid

Since this model exhibits symmetry about the YZPlane, you can divide it in two using a slice operation, and then run the simulation on only one half, to reduce the computing resources required. The slice operation can only be used on geometry which is frozen.

1. Select Tools>Freeze from the Menu Toolbar. 2. Create a new sketch based on Plane5. 3. Use Line from the Draw Toolbox of the Sketching tab to draw a single vertical line in the new sketch, along

the Y-axis. The exact dimensions of the line are not important but the line must extent above the top of the geometry (Y = 20 mm) and below the bottom of the geometry (Y = -20 mm).

4. Select Extrude from the 3D Features Toolbar. 5. Set Base Object to be the new sketch (Sketch2), and set Operation as Slice Material.

6. Set Depth to be 200 mm, and click on Generate to split the pipe. 7. Select Create>Body Operation from the Menu Toolbar. 8. Set Type to Delete and Bodies to the half of the pipe which has its X-coordinate positive, by clicking on it in

the Model View.

9. Click on Generate to remove the unwanted half of the pipe.


Geometry Creation



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Tutorial 6: Butterfly Valve Home Mesh Generation


Mesh Generation

Mesh Generation




Create the region for the inlet:

1. Create a Composite 2D Region called inlet. 2. Select the semi-circular face of the pipe with the lowest Z-coordinate to apply it to.

Create the other regions:

1. Create a Composite 2D Region called outlet on the semi-circular face of the pipe with the highest Z-coordinate.

2. Create a Composite 2D Region called symP on the plane with the highest X-coordinate. 3. Create a Composite 2D Region called pipe wall on the semi-cylindrical pipe wall.

The remaining faces, the faces which form the valve, will be grouped into the Default 2D Region.

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Setting up the Mesh


1. Click on Default Body Spacing in the Tree View, which is contained in Mesh>Spacing. 2. In the Details View, change Maximum Spacing to 4.5 mm, and press Enter on the keyboard to set this

value.

A fine mesh is required around the hinge of the valve and at the top and bottom of the valve plate. In this tutorial, you will use curvature-sensitive meshing. Using this utility, the mesh will automatically be refined in regions where the edges of the surfaces have a large curvature.

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Contents•CopyrightTutorial 6: Butterfly Valve> Mesh Generation

Mesh Generation

1. Click on Default Face Spacing in the Tree View, which is contained in Mesh>Spacing. This is a Face Spacing object which is applied to all faces which do not have a Face Spacing explicitly defined.

2. Set Face Spacing Type to Angular Resolution and set the Angular Resolution to 18 degrees. The mesh will be refined wherever two adjacent surface mesh edges make an angle of more than the number of degrees set by the Angular Resolution setting.

3. Set Minimum Edge Length to 0.5 mm. This prevents over-refinement in areas which have a very large curvature.

4. Set Maximum Edge Length to 4.5 mm and leave the other parameters set to the default settings.

The Face Spacing settings above will produce a fine mesh around the highly-curved parts of the valve. You also need to create another Face Spacing to increase the mesh density in the region near the valve hinge, where the faces are flatter and therefore not refined so much by the Angular Resolution setting.

1. Right-click on Spacing and select Insert>Face Spacing 2. In the Details View, set Face Spacing Type to Constant, and set the Constant Edge Length to 2 mm. 3. Set the Radius of Influence to 0.0 m, and Expansion Factor to 1.3. 4. The four faces which are required for the location are the large flat faces of the valve. These can be quite

tricky to select by just rotating the model and clicking on the faces, so try the following steps: a. In order to better see the inside of the valve, click on Geometry in the Tree View, and in the Details

View, set Transparency to 40 %. b. Click back on the new Face Spacing in the Tree View, and then click in the box next to Location in

the Details View. c. Put the model into the isometric view by clicking on the cyan ball in the triad at the bottom right of

the Model View. Zoom into the valve itself by holding down the Shift key on the keyboard and the middle mouse button, and moving the mouse over the Model View. Position your cursor over the top valve face as shown in the picture below.

d. Now click with the left mouse button as if you wanted to select this face. However, instead you get the symmetry plane selected, since it was that face which was on top. Note that when you click, four rectangles appear in a stack at the bottom left of the model view, as highlighted in the picture below.


Mesh Generation

e. The rectangles represent all of the faces which were under your cursor when you clicked. The top-most one, at the left side of the stack, represents the top face and it is colored red to indicate that this face is selected. You actually wanted to select the next face down, which is represented by the second rectangle from the left. Click on this rectangle to select the top face of the valve.

f. Select the three flat faces on the other side of the valve by holding down Ctrl and clicking on them. You may need to rotate the model slightly to make it possible to pick all three.

5. Press Apply in the Details View. You should see that the text next to Location now reads 4 2D Regions.

This tutorial uses Surface Proximity to automatically refine the mesh where two faces are close to each other without


Mesh Generation

intersecting.


In general, a value of 2 elements across a gap is not recommended when you want to produce a high quality mesh. A small value is used in this case to minimize the size of the mesh for the tutorial.

Set up Inflated Boundaries on the walls:

1. Click on Inflation in the Tree View. In the Details View, set Number of Inflated Layers to 5. 2. Set Expansion Factor to 1.35. This is a large expansion factor. In general a value of 1.2 is recommended. 3. Change Inflation Option to First Layer Thickness, and set the First Prism Height to 0.5 mm.

The pipe wall is to be modeled as a rough wall with an equivalent sand grain roughness of 0.2 mm. To maintain the validity of the assumptions used in modeling rough walls, it is important that the thickness of the first element off the wall is not much smaller than the equivalent roughness height. In general, a value equal to the roughness height is recommended, which would be 0.2 mm here. It is also important that the mesh length scale does not increase dramatically in the transition from the last inflation layer to the rest of the volume mesh. The value chosen here for the first prism height, combined with the high expansion factor, allows the elements in the inflation layers to expand to a reasonable size before the transition to the rest of the volume mesh. To produce a good mesh for this geometry, a much smaller Maximum Spacing is required, allowing a First Prism Height of 0.2 mm to be used and a smooth transition from the last inflation layer to the bulk volume mesh.

4. In the Tree View, right-click on Inflation and select Insert>Inflated Boundary. 5. For Location, select both pipe wall and Default 2D Region from the Tree View. Hold down the Ctrl key in

order to select the second of these.

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Next, take a look at the mesh on the pipe wall:

1. Right-click over Preview in the Tree View, and select Insert>Preview Group. Change the name of the Preview Group to pipe wall.

2. For Location, select the Composite 2D Region pipe wall from the Tree View. 3. Now right-click over the Preview Group pipe wall in the Tree View, and select Generate This Surface

Mesh. The surface mesh will be generated on just the corresponding faces. 4. Click over the axes in the bottom right corner of the Model View in the position shown in the picture below.

As you move the cursor into this position, the black “-X”-axis will appear (it is not shown by default). This will put the geometry into a good position for viewing the mesh.


Mesh Generation

Notice how the nodes are concentrated around the valve.

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1. Click on Options in the Tree View, and change GTM Filename to PipeValveMesh.gtm. 2. Right-click on Mesh in the Tree View and select Generate Volume Mesh.



You can now work through the CFX-5.7 example “Tutorial 9: Flow Through a Butterfly Valve” using the newly-generated mesh.


Mesh Generation

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Geometry Creation Home Tutorial 7: Catalytic Converter


Tutorial 7: Catalytic Converter


This example shows how to create the geometry and mesh for the inlet pipe and flange for a catalytic converter. The following geometry and meshing features are illustrated:

● the Skin/Loft operation to extrapolate between sketch profiles; ● Sketch Instances (copying and pasting an entire sketch); and ● Inflation.

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Geometry Creation

Geometry Creation


1. Open ANSYS Workbench, and create a new project. 2. Open up DesignModeler, specifying the units as centimeters.

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Creating the Sketches for the Inlet Flange

The first geometry operation will be to create four sketches to define the profile of the inlet flange. Two of the sketches are circles, and the other two consist of a more elongated shape constructed from eight edges (lines and curves). You will then use the Skin/Loft operation to connect the sketches. This operation requires that all sketches have the same number of edges, so the two circles will also have to be constructed with eight edges, and at an orientation which gives the smoothest connecting surface when the Skin/Loft operation is applied.

1. Create a new sketch ( ) based on the XYPlane. 2. Use Circle from the Draw Toolbox of the Sketching tab to create the circle centered on the origin with a

radius of 2.5 cm. 3. To break the circle into eight edges, use the Modify Toolbox of the Sketching tab. Click on Split, then right-

click on the Model View and select Split Edge into n Equal Segments. 4. Back on the Sketching tab, next to where you clicked on Split, you will now find a box which allows you to

specify how many segments to break the circle into. Set it to 8 and select the circle in the Model View to perform the Split operation.

To re-orient the circle to give a smoother final surface, you will move it round by 22.5 degrees.

1. Select Move from the Modify Toolbox. In the two boxes which appear, set the rotation angle r to be 22.5 degrees and leave the scale factor f unchanged.

2. Select all eight curves by clicking on them in turn (you don't need to hold down any mouse button to do this). 3. Right-click over the Model View and choose End/Use Plane Origin as Handle. This tells DesignModeler

that you have finished selecting the edges to copy, and that you want to use the origin of the plane as a reference point for the rotation and the paste action which follows.

4. Right-click in the Model View and select Rotate by r Degrees to perform the rotation (you won't see any effect of this yet since it is only actually applied when you paste the circle into its new position).

5. Right-click again and select Paste at Plane Origin. You should see the original circle move round by 22.5 degrees. No translation took place since you pasted the reference point (the origin of the plane/center of the

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Contents•CopyrightTutorial 7: Catalytic Converter> Geometry Creation

Geometry Creation

circle) back at the Plane Origin. 6. Right-click again and select End.

The second sketch, Sketch2, is the second circle, placed in a different plane and made slightly bigger. Rather than constructing it from scratch and having to perform the Split and Move as you did for Sketch1, you will just copy it from Sketch1.

1. Create a new plane ( ), based on the XYPlane. 2. In the Details View, set Transform 1 to Offset Z, and set the Value of the offset to 1 cm.

3. Click on Generate to create the plane. 4. Right-click on Plane4 in the Tree View and select Insert>Sketch Instance. A Sketch Instance is just a copy

of an ordinary sketch. 5. In the Details View, set Base Sketch to Sketch1. 6. Set Scale to 1.05.

7. Click on Generate to create the Sketch Instance. 8. To be able to see both sketches, right-click on each in turn in the Tree View, and select Keep Visible.

You should now be able to see clearly both sketches, offset from each other and with the second one slightly larger than the first.

The next sketch, Sketch3, is a different shape constructed of straight edges and quarter-circles.

1. Create a new plane ( ), based on the XYPlane. 2. In the Details View, set Transform 1 to Offset Z, and set the Value of the offset to 5 cm.

3. Click on Generate to create the plane. 4. Use Grid from the Settings Toolbox of the Sketching tab to set Show in 2D and Snap to on. 5. Set Major Grid Spacing to 5 cm and Minor-Steps per Major to 5. 6. Use the Draw Toolbox of the Sketching tab to construct the shape shown below. For reference, the shape is

20 cm long and 12 cm high, and is orientated with the X-axis along the long axis of the shape.


Geometry Creation

a. Use Line to draw the four straight edges. b. Use Arc by Tangent to draw the four quarter-circles. In each case, select the two end points of the

arc. If the wrong part of the arc is being drawn (i.e. a 270 degree segment instead of a 90 segment) just before you click on the second end point, then right-click and select Reverse to correct it.

Sketch4 is just a copy of Sketch3.

1. Create a new plane ( ), based on the XYPlane. 2. In the Details View, set Transform 1 to Offset Z, and set the offset to 6 cm.

3. Click on Generate to create the plane. 4. Right-click on Plane6 in the Tree View and select Insert>Sketch Instance. A Sketch Instance is just a copy

of an ordinary sketch. 5. In the Details View, set Base Sketch to Sketch3. 6. Set Scale to 1.05.

7. Click on Generate to create the Sketch Instance. 8. To be able to see all four sketches, right-click on the last two in turn in the Tree View, and select Keep

Visible.

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Creating the Inlet Flange

Having created all four profiles, you can now create the solid which connects them by using the Skin/Loft operation.

1. Click on the blue Z-axis in the triad at the bottom right of the Model View to put the geometry into a good viewing position for the selection.

2. Select Skin/Loft from the 3D Features Toolbar. 3. Select the four profiles from the Model View by selecting the four edges shown in the picture below. You

will need to hold down the Control key whilst selecting the second and subsequent edges. Select the edges in the correct order by taking the inside one first and then working outwards: the order of the profiles is important because the Skin/Loft operation will make a surface which smoothly interpolates between them in the order which you specify.


Geometry Creation

4. Click on Apply after selecting the four profiles.

You will now be able to see some gray lines connecting the vertices of the profiles, one vertex from each. (Your gray lines may be in slightly different places, depending on exactly which edges you created first in the different sketches.) These lines are called guide lines, and give you a preview of how the Skin/Loft operation will connect these vertices. Unfortunately, the gray lines in the picture above indicate that the wrong vertices are being connected: if you went ahead and created the solid without fixing this, then the resulting shape would be very twisted. The correct way to join the vertices is shown in the picture below.

Unless your vertices happen to be connected like the ones in the picture above, you will need to fix the problem, as described below.

1. Right-click and select Fix Guide Line.


Geometry Creation

2. Select different edges on the sketches until the gray lines look correct.

Now continue to specify the settings for the Skin/Loft operation.

1. In the Details View for the Skin/Loft, set Merge Topology? to Yes. If you leave it as the default (No), then the solid which is created has 26 surfaces (a planar surface from the edges in Sketch1, a planar surface from the edges in Sketch4, and 24 surfaces for the smooth curved surfaces interpolated between the profiles). If you were to put a mesh onto this solid, then you would have to use a small mesh size to get a good quality mesh on and near the smallest surfaces. However, if you choose to Merge Topology directly in DesignModeler, then the resulting solid only has three surfaces: the smooth curved surface is created in one piece rather than 24 pieces. This solid can be meshed more evenly even with a coarser mesh size.

2. Click on Generate to create the Skin/Loft.

The solid should look like the picture below when appropriately orientated. See the notes below if the solid does not look correct or if you get error messages when you generate it.

If your solid is not correct, try the following.

● Check that each of the four sketches has exactly eight edges, particularly if you get messages about profiles not having an equal number of edges. You can easily do this by selecting each sketch in the Tree View and reading the number of edges in the sketch from the Details View.

● Check that you have selected the profiles in the right order, particularly if you get messages about self-intersecting geometry. You can check the order by viewing the Details View for the Skin/Loft; the profiles are listed in the order of selection. Only the order 1-2-3-4 or 4-3-2-1 will allow the solid to be generated correctly. If your profiles are in the wrong order, then fix this as follows:

1. Right-click on Skin1 in the Tree View and choose Edit Selections. 2. In the Details View, right-click on the name of the profile which is in the wrong order (e.g. Profile2),

and use the commands Move to Top, Move up, Move down, and Move to Bottom to change the position of the profile.

3. Click on Generate to modify the Skin/Loft. ● If you get a solid created which is very twisted, then check that the guide lines are correct: see above for

details. ● If your solid is generated but looks to be the wrong shape, then you will have to check that each profile is


Geometry Creation

correctly positioned, and that the planes you created (Plane4, Plane5 and Plane6) have the correct offsets and are all based on the XYPlane. You should also check that you have selected all four profiles and haven't missed one.

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Creating the Inlet Pipe

You can now create the inlet pipe which attaches to the flange which you have just created. This is in two sections: a curved section and an extruded straight section.

The curved section of the pipe is a Revolve operation based on Sketch1. However, you need to create a line to act as the axis for the rotation first.

1. Create a new sketch ( ) based on the XYPlane. 2. Use Line from the Draw Toolbox of the Sketching tab to draw a line which is parallel to the Y-axis, at X =

15 cm. The length of the line is unimportant.

3. Select Revolve from the 3D Features Toolbar. 4. Set Base Object to Sketch1 and Axis to the line which you have just drawn (which will be selected by

default). 5. Set Direction to Reversed and Angle to 45 degrees.

6. Click on Generate to extrude the inlet pipe.

Finally, you can extrude to make the straight section of the pipe. However, you need to extrude from the end surface of the pipe, which isn't currently defined as a sketch or plane, so first you need to construct the appropriate plane.

1. Create a new plane ( ).


Geometry Creation

2. Set Type to be From Face and Subtype to be Outline Plane. 3. Set Base Face to be the end of the pipe section which you have just created. This can be selected directly by

clicking on it in the Model View.


5. Select Extrude from the 3D Features Toolbar. 6. Set Base Object to be the plane that you have just created (Plane7) and Depth to 10 cm.

7. Click on Generate to create the extrusion.



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Tutorial 7: Catalytic Converter Home Mesh Generation


Mesh Generation

Mesh Generation




In this case, two 2D Regions are required, one on the end of the pipe to allow an Inlet or Outlet Boundary Condition to be applied and a second on the end of the flange to allow an Interface to be created between the flange and catalyst housing.

1. Create a Composite 2D Region called PipeEnd on the circular face at the end of the pipe. 2. Create a Composite 2D Region called FlangeEnd on the planar face at the end of the flange, with the highest

Z-coordinate.

The remaining faces will be grouped into the Default 2D Region.

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Setting up the Mesh


1. Click on Default Body Spacing in the Tree View, which is contained in Mesh>Spacing. 2. In the Details View, change Maximum Spacing to 1.0 cm, and press Enter on the keyboard to set this value.

You can use Inflation to produce a thin layer of prismatic elements along the walls of the converter.

1. Click on Inflation in the Tree View. In the Details View, set Number of Inflated Layers to 5. 2. Leave the rest of the parameters as their default values. 3. In the Tree View, right-click on Inflation and select Insert>Inflated Boundary. 4. For Location, select Default 2D Region from the Tree View. 5. Set Maximum Thickness to 0.5 cm.

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Contents•CopyrightTutorial 7: Catalytic Converter> Mesh Generation

Mesh Generation

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1. Click on Options in the Tree View, and change GTM Filename to CatConvMesh.gtm. 2. Right-click on Mesh in the Tree View and select Generate Volume Mesh.



You can now work through the CFX-5.7 example “Tutorial 10: Flow in a Catalytic Converter” using the newly-generated mesh.

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Geometry Creation Home Tutorial 8: Annulus

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Tutorial 8: Annulus

Tutorial 8: Annulus

This is a very simple example which shows how to mesh a two-dimensional geometry. The following geometry and meshing features are illustrated:

● Inflation.

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http://www.ansys.com/dm_how_tos/cm_non_newton.html2005-2-20 21:07:58

Tutorial 8: Annulus


Geometry Creation

Geometry Creation


1. Open ANSYS Workbench, and create a new project. 2. Open up DesignModeler, specifying the units as feet.

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Creating the Solid

1. Create a new sketch ( ) based on the XYPlane. 2. Use Grid from the Settings Toolbox of the Sketching tab to set Show in 2D and Snap to On. 3. Set Major Grid Spacing to 0.5 ft and Minor-Steps per Major to 4. 4. Use Circle from the Draw Toolbox of the Sketching tab to create a circle centered on the origin with a radius

of 0.5 ft. 5. Use Circle again to create another circle centered on X = 0 ft, Y = 0.125 ft, with a radius of 0.75 ft.

6. Select Extrude from the 3D Features Toolbar. 7. Set Base Object to be the sketch that you have just created (Sketch1) and Depth to 0.1 ft.

8. Click on Generate to create the solid.



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Tutorial 8: Annulus Home Mesh Generation

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Contents•CopyrightTutorial 8: Annulus> Geometry Creation

Mesh Generation

Mesh Generation




Create the 2D Regions:

1. Create a Composite 2D Region called rotwall on the inner wall, which will subsequently be rotating in the CFD simulation.

2. Create a Composite 2D Region called SymP1 on the planar face with the lowest Z-coordinate. 3. Create a Composite 2D Region called SymP2 on the planar face with the highest Z-coordinate.

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Setting up the Mesh


1. Click on Default Body Spacing in the Tree View, which is contained in Mesh>Spacing. 2. In the Details View, change Maximum Spacing to 0.05 feet, and press Enter on the keyboard to set this

value.

A fine mesh is required on the inner and outer radius walls to resolve the shear layers and accurately predict the viscosity variation in the boundary layer regions. You will use inflation to create layers of prismatic elements on the Wall boundaries.

1. Click on Inflation in the Tree View. In the Details View, set Number of Inflated Layers to 10. 2. Set Expansion Factor to 1.3. Leave the rest of the parameters as their default values. 3. In the Tree View, right-click on Inflation and select Insert>Inflated Boundary. 4. For Location, select Default 2D Region and rotwall from the Tree View. 5. Set Maximum Thickness to 0.05 feet.

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Contents•CopyrightTutorial 8: Annulus> Mesh Generation

Mesh Generation



1. Click on Options in the Tree View, and change GTM Filename to NonNewtonMesh.gtm. 2. Right-click on Mesh in the Tree View and select Generate Volume Mesh.



You can now work through the CFX-5.7 example “Tutorial 11: Non-Newtonian Fluid Flow in an Annulus” using the newly-generated mesh.

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Geometry Creation Home Tutorial 9: Mixing Tube

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Tutorial 9: Mixing Tube


This is a simple example which shows how to add extra surfaces to a model which can then be used for boundary conditions. The picture above shows the geometry: the three circular holes will be used in the final CFD simulation to inject the reactants to be mixed, and they must exist as distinct surfaces to allow the inlet boundary conditions to be defined in the simulation. The following geometry and meshing features are illustrated:

● Imprint Surfaces, to add surfaces for boundary conditions; ● curvature-sensitive meshing; ● Inflation; ● Stretch, to reduce the number of elements along one axis; and ● Preview Groups, to view part of the surface mesh.

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Geometry Creation

Geometry Creation


1. Open ANSYS Workbench, and create a new project. 2. Open up DesignModeler, specifying the units as millimeters.

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Creating the Solid

The first step is to create the solid for the mixing tube.

1. Create a new sketch ( ) based on the XYPlane. 2. Use Rectangle from the Draw Toolbox of the Sketching tab to create a rectangle which extends from 0 < X <

60 mm and -10 mm < Y < -4 mm.

3. Select Revolve from the 3D Features Toolbar. 4. Set the axis for the rotation as follows. First, click on the line which forms the bottom of the rectangle (Y = -

10 mm), and then click on Apply in the Details View. 5. Set Direction to Both - Symmetric and Angle to 15 degrees.


Notice that the curved surface of the solid consists of just one surface, as can be seen by clicking on it.

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Contents•CopyrightTutorial 9: Mixing Tube> Geometry Creation

Geometry Creation

Breaking up the Curved Surface

You need to break up this surface so that the three circular holes are created as separate surfaces. The basic method to do this is to create a sketch containing the three circles, and then to Extrude with Imprint Surfaces to effectively project the circles onto the full curved surface.

1. Create a new sketch ( ) based on the ZXPlane. [In ANSYS Workbench 8.0.1, base the new sketch on the XZPlane.]

2. Use Circle from the Draw Toolbox of the Sketching tab to create three circles in this sketch, as shown below. The circles each have radius 0.75 mm, and their centers are positioned 5 mm, 15 mm and 25 mm from the X-axis respectively. Note that if you draw the circles sufficiently close to having an equal radius (before attempting to add dimensions to specify the radii more precisely) then DesignModeler will apply an Auto Constraint to the circles, constraining their radii to be equal. If this happens, then you will see a warning: “New dimension makes model over-constrained.” when you try to dimension the radius of the second or subsequent circle. If you do see this warning, then click OK to clear the warning and then right-click over the Model View and select Cancel. You will not need to set a dimension on this circle in this case: its radius will always be identical to the radius that you have already set.

Now you can create the Extrude.

1. Select Extrude from the 3D Features Toolbar. 2. Set Base Object to be the new sketch (Sketch2), and set Operation to Imprint Faces. 3. Set Direction to Reversed, Type to be To Faces, and select the curved surface as the Target Face. [In

ANSYS Workbench 8.0.1, Direction should be set to Normal.]

4. Click on Generate to break up the surface.

You should now find that if you click on the curved surface of the solid, it consists of four separate surfaces: the three circles and the remainder.


Geometry Creation



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Tutorial 9: Mixing Tube Home Mesh Generation


Mesh Generation

Mesh Generation





1. Create a Composite 2D Region called InWater on the nearly-triangular face with the lowest X-coordinate. 2. Create a Composite 2D Region called InAcid on the circular face nearest to the InWater 2D Region which

you have just created. The circle is part of the curved face of the reactor. 3. Create a Composite 2D Region called InAlkali on the two remaining circular faces. 4. Create a Composite 2D Region called out on the nearly-triangular face with the highest X-coordinate. 5. Create a Composite 2D Region called sym1 on the planar face with the higher Z-coordinates. 6. Create a Composite 2D Region called sym2 on the planar face with the lower Z-coordinates.

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Setting up the Mesh


1. Click on Default Body Spacing in the Tree View, which is contained in Mesh>Spacing. 2. In the Details View, change Maximum Spacing to 0.6 mm, and press Enter on the keyboard to set this

value.

A fine mesh is required around the circular inlets. In this tutorial, you will use curvature-sensitive meshing. Using this utility, the mesh will automatically be refined in regions where the edges of the surfaces have a large curvature.

1. Click on Default Face Spacing in the Tree View, which is contained in Mesh>Spacing. This is a Face Spacing object which is applied to all faces which do not have a Face Spacing explicitly defined.

2. Set the Angular Resolution to 18 degrees. The mesh will be refined wherever two adjacent surface mesh edges make an angle of more than the number of degrees set by the Angular Resolution setting.

3. Set Minimum Edge Length to 0.15 mm. This prevents over-refinement in areas which have a very large curvature.

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Contents•CopyrightTutorial 9: Mixing Tube> Mesh Generation

Mesh Generation

4. Set Maximum Edge Length to 0.6 mm and leave the other parameters to the default settings.

Since the geometry is long and thin, it is appropriate to generate a stretched mesh to expand the mesh elements in the X-direction. In practice, the geometry is expanded by the specified factors, meshing takes place and then the geometry is contracted back to its original size. This results in fewer elements along the length of the reactor without affecting how many elements are present in a cross-section of the tube.

1. Click on Stretch in the Tree View. 2. Set Stretch in X to 0.5 and leave the other stretch factors set to 1.

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To see the effects of curvature-sensitive meshing, preview the surface mesh on the wall of the reactor.

1. Right-click over Preview in the Tree View, and select Insert>Preview Group. Change the name of the Preview Group to wall.

2. For Location, select the Composite 2D Region Default 2D Region from the Tree View. 3. Now right-click over the Preview Group wall in the Tree View, and select Generate This Surface Mesh.

The surface mesh will be generated on just the corresponding faces. 4. Zoom into the area around the three circular inlets by clicking with the right mouse button and dragging a

zoom box over the area required.

You will see that the mesh has been automatically refined around the three inlets.

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It is a good idea to put inflation on the reactor wall.

1. Click on Inflation in the Tree View. In the Details View, set Number of Inflated Layers to 5. 2. Set Expansion Factor to 1.3. Leave the rest of the parameters as their default values. 3. In the Tree View, right-click on Inflation and select Insert>Inflated Boundary. 4. For Location, select Default 2D Region from the Tree View. 5. Set Maximum Thickness to 0.6 mm.


Mesh Generation

Back To Top



1. Click on Options in the Tree View, and change GTM Filename to ReactorMesh.gtm. 2. Right-click on Mesh in the Tree View and select Generate Volume Mesh.



You can now work through the CFX-5.7 example “Tutorial 13: Reacting Flow in a Mixing Tube” using the newly-generated mesh.

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Geometry Creation Home Tutorial 10: Heating Coil


Tutorial 10: Heating Coil


This example creates the geometry and mesh for a heating coil, which consists of a solid copper coil in a vessel containing liquid. Two solid bodies are required, one for the coil and one for the containing vessel. The following geometry and meshing features are illustrated:

● the Sweep operation to create the coil; ● multiple solid bodies; ● Body Operations; ● Face Spacing, to refine the mesh on a particular face; ● Inflation; ● Proximity; and ● Preview Groups, to view part of the surface mesh.

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Geometry Creation

Geometry Creation



Back To Top

Creating the Profile and Path

You will use the Sweep action to create the coil, and this requires sketches to define the profile (the circle which forms the cross-section for the coil) and the path around which it will be swept.

1. Create a new sketch ( ) based on the YZPlane. 2. The sketch needs to contain a circle with radius 0.1 m and centered on Y = 0.75 m, Z = 0.5 m. Set up the grid

to have a Major Grid Spacing of 1 m and Minor-Steps per Major of 4 to help you position the center of the circle.

3. Use Circle from the Draw Toolbox of the Sketching tab to create the circle centered on Y = 0.75 m, Z = 0.5 m with any convenient radius. Then adjust the radius to 0.1 m by using the Dimensions section of the Sketching tab.

4. This example will split the circle into two pieces, for reasons which will be explained later on. To break the circle into two pieces, use the Modify Toolbox of the Sketching tab. Click on Split, then right-click on the Model View and select Split Edge into n Equal Segments.

5. Back on the Sketching tab, next to where you clicked on Split, you will now find a box which allows you to specify how many segments to break the circle into. Set it to 2 and select the circle in the Model View to perform the Split operation.

6. Create another new sketch ( ), Sketch2, also based on the YZPlane. 7. Use the Line tool from the Sketching tab to create a single straight line along the Z-axis, from Z = 0.5 m to Z

= 1.5 m.

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Using Sweep to Make the Coil

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Contents•CopyrightTutorial 10: Heating Coil> Geometry Creation

Geometry Creation

1. Select Sweep from the 3D Features Toolbar. 2. Set the Profile to be Sketch1: click on Sketch1 in the Tree View and then click on Apply in the Details

View at the bottom-left of the screen. 3. Set the Path to Sketch2: click on the Not selected text next to Path, click on Sketch2 in the Tree View, and

then click on Apply. 4. Set the Scale to 1. 5. Set the number of Turns to 2.

6. Click on Generate to create the coil.

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Extruding the Bottom End of the Coil

If you look at the full picture of the geometry at the top of this example, you will be able to see that the ends of the coil are extruded to the edges of the container. However, the extrusion is not normal to the faces at the end of the coil: if you were to extrude in the normal direction then the coil would look like the picture (a) below, whereas the actual coil is shown in picture (b).


Geometry Creation

(a) (b)

To create the extrusion in a direction which is not normal to the faces, you need to define a vector which gives the direction for the extrude. The way that you will create the vector here is to calculate explicitly the angle at which the extrusion takes place to maintain the smooth gradient from the main coil into the extrusion. Straightforward trigonometry shows that the angle between the path and the horizontal is 6.06 degrees:

1. Create a new sketch ( ) based on the ZXPlane. [In ANSYS Workbench 8.0.1, create the new sketch based on the XZPlane.]

2. Use Line from the Draw Toolbox of the Sketching tab to create the line. To position it, place the first point at Z = 0 m, X = 0 m and then put the second point down at approximately the correct angle, as shown in the picture below. [In ANSYS Workbench 8.0.1, make the length of the line at least 1 m long. In ANSYS Workbench 8.1, the length is not important.]

3. Now specify the exact angle as follows. Use the Dimensions section of the Sketching tab, and choose Angle. Then click on the line and then on the X-axis. If the wrong angle is displayed after you have selected the axis, then right-click and choose Alternate Angle until the correct angle is displayed. Click in the Model View to position the angle label. Finally, type the angle, 6.06 degrees, into the Dimensions box in the Details View.


Geometry Creation

In ANSYS Workbench 8.1, the Extrude operation can be used for this extrusion. [See below for instructions for ANSYS Workbench 8.0.1.]

1. Select Extrude from the 3D Features Toolbar. 2. Set Base Object to be Sketch1, and set Operation as Add Material. 3. Click on Direction Vector to change it from just being None (Normal). Right-click in the Tree View over

Sketch3, and select Keep Visible, then click on the single line in Sketch3 which defines the direction vector. Press Apply in the Details View. The text should now read 2D Edge.

4. Set Depth to be 1.2 m and Merge Topology? to No. Click on Generate to extrude the bottom end of the coil.

In ANSYS Workbench 8.0.1, Extrude cannot be used for extruding in a direction which is not normal to the faces, and so you must use Sweep. The Sweep operation to make the extrusion at the bottom end of coil can use the original circle (Sketch1) for the profile, and the new sketch (containing just the line) as the path.

1. Select Sweep from the 3D Features Toolbar.

2. Set the Profile to be Sketch1.

3. Set the Path to Sketch3.

4. Set the Scale to 1.

5. Set the number of Turns to 0.

6. Click on Generate to create the sweep.

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Geometry Creation

Extruding the Top End of the Coil

The actions above will be repeated to extrude the top part of the coil. However, there is no existing sketch to use to extrude from. Instead, you will create a new plane from the top circular end of the coil, which can be used for this purpose.

1. Create a new plane ( ). 2. Set Type to be From Face and Subtype to be Outline Plane. 3. Set Base Face to be the circular face at the top of the coil. This can be selected directly by clicking on it in

the Model View.


In ANSYS Workbench 8.1, the Extrude operation can again be used for this extrusion. [See below for instructions for ANSYS Workbench 8.0.1.]

1. Select Extrude from the 3D Features Toolbar. 2. Set Base Object to be Plane4, and set Operation as Add Material. 3. Click on Direction Vector to change it from just being None (Normal). Click on the single line in Sketch3

which defines the direction vector, which is the same as for the previous Extrude. Press Apply in the Details View. The text should now read 2D Edge.

4. Set Direction to Reversed, Depth to 1.2 m, and Merge Topology? to No. Click on Generate to extrude the top end of the coil.

In ANSYS Workbench 8.0.1, you must use Sweep again. You can use the new plane as the profile for the Sweep, but must make a new sketch for the path.

1. Create another new sketch ( ) based on the XZPlane, to form the path for the extrusion at the top.

2. In the new sketch, create a single line starting at X = 0 m, Z = 0 m. The line needs to extend in the opposite direction to the one created in Sketch3, but still making an angle of 6.06 degrees to the X-axis, as shown in the picture below. To specify the same angle as for the previous line, you can use any of the following methods:

● specify the angle directly, as you did for the previous sketch;

● constrain the two lines to be Parallel using the Constraints section of the Sketching tab; or

● draw the line at approximately the right angle and adjust the angle until DesignModeler shows two parallel strokes above the line which you are drawing. If you let go of the mouse button whilst the two parallel strokes are showing, then DesignModeler will automatically constrain the new line to be parallel to the old line.


Geometry Creation

3. Select Sweep from the 3D Features Toolbar.

4. Set Profile to be the new plane (Plane4), and Path to the second angled line (Sketch4).

5. Leave the other settings as their defaults, and click on Generate to create the extrusion.

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Trimming the Ends of the Coil

Now trim the ends of the coil as follows.

1. Create a new sketch based on the XYPlane. 2. Use Circle from the Draw Toolbox of the Sketching tab to draw two circles in the new sketch. Both should

be centered on the origin, and their radii should be exactly 1 m and at least 1.5 m respectively.

3. Select Extrude from the 3D Features Toolbar. 4. Set Base Object to be the new sketch, and set Operation as Cut Material.

5. Set Depth to be 2 m, and click on Generate to remove the ends of the pipes. 6. If one or both of the lines which formed the paths for the previous two extrusion operations was excessively

long, then you might see that although the ends of your pipes are trimmed correctly, there are some parts of the pipes which remain as separate bodies, not connected to the main coil. You can check this easily by looking at the very bottom of the Tree View. If it shows “1 Part, 1 Body”, then your model is fine. If it shows more than one Part or Body, then you need to increase the radius of the outer circle in the sketch so that it removes these extra bodies, as follows:

a. Click on the sketch name in the Tree View. b. Click on Drag from the Modify Toolbox of the Sketching tab. c. Click on the outer circle, and use the mouse to increase its radius.

d. Click on Generate to regenerate the solid body.

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Geometry Creation

Creation of the Container

You have already created the coil, and the next step is to create the container around the coil. DesignModeler has an Enclosure feature which allows the easy creation of a cylindrical enclosure around a solid body and generates the cylinder automatically; however, this only works if the solid body is not required to touch the edges of the enclosure. In this case, the ends of the coil will touch the sides of the container, so although the Enclosure feature can be used, you will have to construct the cylinder manually first.

The first step is to freeze the coil, so that it is not affected by the next geometry creation actions, and to give it a name, so that it can easily be identified later.

1. Select Tools>Freeze.2. In the Tree View, click on the plus sign next to “1 Part, 1 Body” and then select Solid from the tree

underneath this entry. In the Details View, you will now see the information relating to the body. Click on the word “Solid” in this information, and change it to read “Coil”. Pressing Enter on the keyboard will let the name change take effect.

3. Create a new sketch ( ) based on the XYPlane. 4. Use Circle from the Draw Toolbox of the Sketching tab to draw two circles in the new sketch. Both should

be centered on the origin, and their radii should be exactly 1 m and 0.5 m respectively. Since a circle of radius of 1 m already exists in an earlier sketch, you may find that if you try to set the radius of the outer circle to be 1 m using the Dimensions Toolbox, you get a warning: “New dimension makes model over-constrained.” This occurs if DesignModeler has applied Auto Constraints to your new circle, already constraining the radius to be 1 m to match the existing circle. If you do see this warning, then click OK to clear the warning and then right-click over the Model View and select Cancel. You will not need to set a dimension on this circle in this case.

5. Select Extrude from the 3D Features Toolbar. 6. Set Base Object to be the new sketch, and set Operation as Add Material.

7. Set Depth to be 2.25 m, and click on Generate to create the container. 8. In the Tree View, under where it says “2 Parts, 2 Bodies”, click on Solid. In the Details View, click on the

“Solid”, rename it to “Container” and then press Enter on the keyboard.

The next step is to cut the coil out from the container, using the Enclosure feature.

1. Select Tools>Enclosure from the Menu Toolbar. 2. Set Shape to User Defined. 3. Select the container as the User Defined Body. To select it, you can click on Container in the Tree View,

under “2 Parts, 2 Bodies”. 4. Set Merge Parts? to Yes. This ensures that the final bodies are all in one part, and saves you from having to

merge them into one part explicitly later on. The Merge Parts operation is able to operate more reliably if the surfaces which form the interface between the two parts are not just closed loops, and this is the reason for breaking the circle in Sketch 1 into two separate pieces.

5. Click on Generate to cut the coil out from the container.

This operation cuts a coil-shaped hole in the container, without deleting the coil, as required.


Geometry Creation



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Tutorial 10: Heating Coil Home Mesh Generation


Mesh Generation

Mesh Generation





1. Create a Composite 2D Region called inflow on the large annular face with the lowest Z-coordinate. 2. Create a Composite 2D Region called outflow on the large annular face with the highest Z-coordinate.

Finally, you need to create a Composite 2D Region on the coil itself. First, you need to understand an important distinction between 2D Regions and solid faces which applies when there is more than one Solid Body present in the model (which is what we have here: one solid is the coil, and the other is the container). Where two Solid Bodies meet at a common face, there is just one face present in the geometry; however, there are two 2D Regions, as shown in the example below.

If your model has only one solid, then there is no difference between a face and 2D Region. If your model has more than one solid, then all of the external faces will also be 2D Regions. However, 2 2D Regions will exist for every internal (shared) face.

So when you create the Composite 2D Region on the coil, you have to be very clear which side of the face you want to select to include in the 2D Region. Since you are going to be applying Inflation to the 2D Region, you need to select the 2D Regions on the container side of the faces, so that the Inflation grows into the container (where you have fluid flow and need to resolve the boundary well) and not into the coil itself (where there is only heat transfer and no particular need to resolve the boundary fields).

To make the selection, you need to make use of the selection rectangles. The use of these was described for a single solid in the meshing section of Tutorial 6: Butterfly Valve. If you have not already completed this tutorial, it is

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Mesh Generation

recommended that you do so in order to familiarize yourself with the way that the selection rectangles work.

When multiple solid bodies are present, rather than having one selection rectangle per face, one selection rectangle per 2D Region is displayed. You can therefore use these to select the appropriate 2D Regions accurately.

There are three sections of the coil which need to be selected.

1. Right-click over Regions in the Tree View and select Insert>Composite 2D Region. Change its name by right-clicking over its name and typing in coil surface.

2. Click on the green Y-axis in the triad at the bottom right of the Model View to put the geometry into a good viewing position for the selection.

3. In order to better see the inside of the coil, click on Geometry in the Tree View, and in the Details View, set Transparency to 40 %.

4. Click back on the new Composite 2D Region in the Tree View, and then click in the box next to Location in the Details View.

5. Place the cursor in the position shown in the picture below and click with the left mouse button.

6. The selection rectangles will appear and the outside face of the container will be highlighted. The 2D Regions the selection rectangles correspond to are (from left to right): outside of the container, coil surface (container side), coil surface (coil side), inner cylinder. Click on the second one from the left (coil surface, container side), to select it, and then press Apply. In order to see clearly which 2D region you have selected, right-click over Part 3 in the Tree View under Geometry, and select Suppress. Now click on the new region name coil surface to see exactly which face is contains. You should find that it contains a section of coil as shown in the picture below: you may have the top half of the section (shown below) or you may have the bottom section.

7. Now unsuppress Part 3 (by right-clicking on its name in the Tree View), select the Composite 2D Region coil surface and click on 1 2D Region in the Details View. You can now add 2D Regions to the selection.


Mesh Generation

You need to add the other half of the coil section, so hold down Ctrl, click over the Model View over the relevant part of the coil, and use the selection rectangles (still holding down Ctrl) to select the coil surface (still the second rectangle down). If you now press Apply and follow the same procedure as above to hide Part 3 and select coil surface, you should now be able to see that you have both a top and bottom to the coil section, as shown below.

8. Repeat the steps given above to select the two end sections of the coil (two surfaces at each end). In every case, you will need to use the selection rectangles to choose the second surface down. When you have finished, the Location for the Composite 2D Region coil surface should read 6 2D Regions and the regions selected should look like the picture below.

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Setting up the Mesh



1. Right-click on Spacing and select Insert>Face Spacing 2. In the Details View, set Face Spacing Type to Constant, and set the Constant Edge Length to 0.07 m. 3. Set the Radius of Influence to 0.0 m, and Expansion Factor to 1.2. 4. For Location, select the Composite 2D Region coil surface from the Tree View.


Mesh Generation

Note that the Composite 2D Region coil surface only contains one side of the coil faces, not both. The surface mesh is created per face, not per face side, so by setting a Face Spacing on this region, you are implicitly controlling the face spacing on the other sides of the coil faces, which are contained in the Default 2D Region. This implies that you must not attempt to also specify a Face Spacing on the 2D Regions which form the other side of the coil faces.

Proximity will greatly improve the mesh for this tutorial. However, in order to keep the number of elements down for tutorial purposes, the Number of Elements Across Gap is reduced from the recommended number 4 down to 2.


Create an Inflated Boundary on the coil:

1. Click on Inflation in the Tree View. In the Details View, set Number of Inflated Layers to 4. 2. Leave the rest of the parameters as their default values. 3. In the Tree View, right-click on Inflation and select Insert>Inflated Boundary. 4. For Location, select coil surface from the Tree View. 5. Set Maximum Thickness to 0.1 m.

Because only one side of the faces which form the boundary between the coil and container are contained in coil surface, Inflation will only take place on the container side of the faces.

Back To Top


You can check your inflation layer to ensure that you selected the correct sides of the faces for Inflation.

1. Right-click over Preview in the Tree View, and select Insert>Preview Group. Change the name of the Preview Group to coil.

2. For Location, select the Composite 2D Region coil surface from the Tree View. 3. Now right-click over the Preview Group coil in the Tree View, and select Generate This Surface Mesh. The

surface mesh will be generated on just the corresponding faces. 4. Click on Generate Options under Preview in the Tree View, and set Show Inflated Front to Yes. Now,

when you generate the surface mesh, CFX-Mesh will actually show you the mesh on the top of the inflated layers, rather than on the geometrical surfaces. This will allow you to check where the inflation is taking place.

5. Right-click over the Preview Group coil in the Tree View, and select Generate This Surface Mesh. The surface mesh will be generated on the top of the inflated layers.

Your mesh should look like the picture below i.e. the inflated layers are all outside the coil and of a uniform thickness.


Mesh Generation

If, however, you selected one of the 2D Regions incorrectly, you may get a picture which is more like the one below:

This picture shows that the inflation layers actually go inside the coil at the top right of the picture. In fact, one of the coil faces in this part of the coil was selected incorrectly. If your mesh is incorrect, then go back and re-select the 2D Regions for the Composite 2D Region coil surface.

You may find that the surface mesh generation process produces warnings about poor angles. This indicates that the mesh is not of a high quality, and it is the result of meshing this geometry with over-coarse length scales (in order to keep the solution time down for tutorial purposes).

Now create another Inflated Boundary on the wall of the container:

1. In the Tree View, right-click on Inflation and select Insert>Inflated Boundary. 2. For Location, select the outside and inside walls of the container (the large cylindrical face and the inner

cylindrical face) from the Model View. 3. Set Maximum Thickness to 0.1 m.


Mesh Generation

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1. Click on Options in the Tree View, and change GTM Filename to HeatingCoilMesh.gtm. 2. Right-click on Mesh in the Tree View and select Generate Volume Mesh.



You can now work through the CFX-5.7 example “Tutorial 14: Conjugate Heat Transfer in a Heating Coil” using the newly-generated mesh.

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Geometry Creation Home Tutorial 11: Airlift Reactor


Tutorial 11: Airlift Reactor


This example creates the geometry and mesh for an airlift reactor or bubble column. The two figures above show the geometry created in DesignModeler (left) and a schematic picture of the full geometry, not to scale (right). In the CFD simulation, the air is input through a small ring sparger. It then rises up to the top of the geometry and leaves the reactor. A thin draft tube helps to stabilize the rising plume of bubbles. The full geometry is rotationally symmetric, so only a 30-degree segment needs to be modeled.

The draft tube will modeled as a “thin surface” (which has no thickness), and so it must be created as an internal face of a separate body, which will need to be created in DesignModeler. The following geometry and meshing features are illustrated:

● multiple solid bodies; ● Imprint Surfaces, to add surfaces for boundary conditions; and ● Face Spacing, to refine the mesh on a particular face.

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Geometry Creation

Geometry Creation



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Creating the Main Solid

The first step is to create the main solid.

1. Create a new sketch ( ) based on the XYPlane. 2. Use Polyline from the Draw Toolbox of the Sketching tab to create a closed polyline in the shape shown

below (the Y-axis is vertical). To close the polyline, right-click over the Model View after you have selected the last point and select Closed End.

3. Use Circle from the Draw Toolbox to create the circle shown in the diagram. 4. Use the Dimensions Toolbox of the Sketching tab to add the dimension labels H1, H2, etc. shown in the

picture. It does not matter if your labels do not have the same names as the ones in the picture. You will need to use the Horizontal, Vertical and Radius items from this Toolbox to label the “H”, “V” and “R” dimensions, respectively.

5. To ensure that the length of the bottom of the reactor is the same as the length of the top (H1), select Equal Length from the Constraints Toolbox of the Sketching tab, and then select the top and bottom edges of the

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Geometry Creation

sketch. This ensures then when you set (or change) the dimension H1, both top and bottom of the reactor are affected.

6. Now use the table below to assign actual lengths to the dimensions listed in the Details View. Since the original sketch is not to scale, you will find that the geometry changes shape as you apply each one, particularly when you specify the bubble column height.

Dimension label in picture above Length

Column radius H1 8.0 cm

Distance between draft tube and outside of column H2 2.5 cm

Distance between axis and sparger H3 3.0 cm

Height of column V4 77.0 cm

Distance between top of draft tube and column top V5 3.5 cm

Distance between bottom of draft tube and column base V6 3.5 cm

Height of sparger above column base V7 3.5 cm

Radius of sparger R8 0.4 cm

Now you can use this sketch to create the solid body.

1. Select Revolve from the 3D Features Toolbar. 2. Set the axis for the rotation by clicking on the Y-axis and then clicking on Apply in the Details View. 3. Leave Direction set to Normal and Angle set to 30 degrees.


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Breaking the Sparger Surface to form the Inlet

When the CFD simulation is run, the gas is injected through the top of the small circular hole, through a 74-degree segment. Currently, the hole is defined with just one surface, so this must be broken to allow the boundary conditions to be appropriately defined. The steps below explain how to modify the solid to achieve this. All of this could have been done as part of the original construction of the solid, but this tutorial has split the steps up to make it clear exactly what each step achieves.

1. The display will be clearer for the next step if you hide the solid for now: double-click on 1 Part, 1 Body in the Tree View, right-click on Solid, and choose to Hide Body.

2. Select Sketch1 from the Tree View and go to the Modify Toolbox of the Sketching tab. 3. Click on Split, and break the circle into two parts by clicking on it in approximately the positions shown

below in the picture below. The exact position of the breaks does not matter for the moment, but make sure that you don't choose break points which are exactly at the highest or widest points of the circle.


Geometry Creation

Simply breaking the circle into two parts and regenerating the solid isn't enough to make the hole have two surfaces. This is because by default, the Revolve operation is set to use Merge Topology? as Yes. This has the effect of optimizing the topology of the resulting solid, which in this case means that the hole is always created as just one surface.

1. Select the Revolve1 object from the Tree View. 2. Set Merge Topology? to No.

3. Click on Generate to apply the changes to the solid. 4. Show the solid again by right-clicking on Solid in the Tree View, and choosing to Show Body.

You should now find that the hole in the solid has two faces as required.

The final step in the construction of this solid is to position the two breaks in the circle in the correct location. As before, this could have been combined with the earlier steps, but it is clearer to separate it out for the purposes of the tutorial. To position the breaks correctly, you will create a second sketch which is not used to generate a solid directly but acts to constrain the breaks in the circle.

1. Hide the solid again by right-clicking on Solid in the Tree View, and choosing to Hide Body.

2. Create a new sketch ( ) based on the XYPlane. 3. Zoom into the circle from Sketch1 by clicking with the right mouse button somewhere near the circle and

dragging a box over it whilst holding down the mouse button. 4. Use Line from the Draw Toolbox of the Sketching tab to draw a vertical line with one endpoint at the center

of the circle in Sketch1. You can make sure the line starts on the existing center point by ensuring that as you click the mouse button on it, a letter “P” appears next to the cursor. This tells you that you are choosing an existing point and not creating a new point. For the second point, move the cursor approximately vertically upwards and adjust it until a “V” appears next to the line. If you click whilst the “V” shape is present then the line is automatically constrained to be vertical. The length of the line does not matter, since you are only going to use it to define a symmetry axis.

5. Now draw two more lines, connecting each of the two vertices on the circle (where you split it) to the center of the circle. Again, you can make sure the lines start and finish on the existing points by ensuring that as you click the mouse button on the appropriate point, a letter “P” appears next to the cursor.

6. The next step is to constrain the points so that they are symmetrically placed on each side of the vertical line. Select the Constraints Toolbox of the Sketching tab, and click on Symmetry. Click first on the vertical line to pick the symmetry axis, and then click on the two straight lines to position them symmetrically.


Geometry Creation

This move the points in the Sketch2 to be symmetric about the vertical line. However, when you created these points you defined them to be coincident points with the breaks in the circle in Sketch1, so this operation will also move the circle breaks in Sketch1 to be symmetric.

1. Select Angle from the Dimensions Toolbox of the Sketching tab 2. Set the angle between the two lines to be 74 degrees. If the wrong angle is displayed after you have selected

the second line, then before you click to fix the label, right-click and choose Alternate Angle until the correct angle is displayed.

1. Click on Generate to modify the solid. 2. Show the solid again by right-clicking on Solid in the Tree View, and choosing to Show Body.

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Creating the Second Solid


Geometry Creation

Now what remains is to create the second solid, which fills in the gap at the outside of the reactor. If you just ask to create another solid, then the operation Add Material will add material to the first solid rather than creating a second solid as desired. The way to avoid this is to use Add Frozen instead of Add Material. Then the solid creation operation, Extrude in this case, will add a new, separate solid. A frozen solid is not affected by most geometry operations that follow, and will appear by default as slightly transparent.

To create the second solid, you first need to create a plane to extrude from.

1. Make sure that no faces are selected, and then create a new plane ( ). 2. Set Type as From Face and check that Subtype is set to Outline Plane. If Subtype is already set to

Tangent Plane, then you will not be able to change it: delete the new plane, make sure that no faces are selected (by clicking somewhere in the Model View away from the geometry) and create a new plane instead.

3. For the Base Face, select the horizontal face at 3.5 cm above the bottom of the reactor - see the picture below - and then click on Apply in the Details View.


1. Select Extrude from the 3D Features Toolbar. 2. Set Operation to Add Frozen. 3. Set Type to To Faces. This will make the Extrude stop when it reaches the selected face(s). 4. Set the Target Face as the horizontal surface which is 3.5 cm below the top of the reactor



Geometry Creation

The Tree View should now show that you have 2 Parts, 2 Bodies. In order to produce a single mesh on the two bodies, they must be combined into one part.

1. From the Selection Toolbar at the top of the window, turn on Select Bodies ( ). This means that you can only select Solid Bodies in the next operation, which helps to make the selection process easier.

2. In the Model View, select one of the two Bodies by clicking on them with the left mouse button. Hold down the Ctrl key and then click on the other one in order to add to the original selection.

3. Right-click over the Model View and select Form New Part.



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Tutorial 11: Airlift Reactor Home Mesh Generation


Mesh Generation

Mesh Generation





1. Create a Composite 2D Region called Sparger on the top part of the small hole (the ring sparger). 2. Create a Composite 2D Region called Top on the very top face of the reactor (highest Y-coordinate). 3. Create a Composite 2D Region called Column on the column walls. You need to select five faces: the three

parts of the outside wall (highest X-coordinate), the bottom face of the reactor (lowest Y-coordinate) and the bottom part of the small hole which forms the ring sparger.

4. Create a Composite 2D Region called Symmetry1 on the two faces which lie in the XYPlane. 5. Create a Composite 2D Region called Symmetry2 on the two faces which are directly opposite the faces

used for Symmetry1.

Finally, create a Composite 2D Region on the internal face which will form the draft tube. In order to do this, it is important to understand the difference between faces and 2D Regions when there are multiple solids in the geometry, and how to use the selection rectangles. If you have not already done so, you are advised to work through or at least read the meshing section of Tutorial 6: Butterfly Valve and the meshing section of Tutorial 10: Heating Coil.

For the Composite 2D Region which comprises the draft tube, it is appropriate to include only one side of the internal face. When you come to set up the Thin Surface boundary condition in CFX-Pre, the other side of the face will then be automatically identified as the other side of the thin surface.

1. Right-click over Regions in the Tree View and select Insert>Composite 2D Region. Change its name by right-clicking over its name and typing in DraftTube.

2. Click on the cyan ball in the triad at the bottom right of the Model View to put the geometry into a good viewing position for the selection.

3. Click next to Location in the Details View, ready to make the selection. 4. Place the cursor in the position shown in the picture below and click with the left mouse button.

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Mesh Generation

5. The selection rectangles will appear. The 2D Regions they correspond to are (from left to right): outside of the column, draft tube face (outside), draft tube face (inside), face from symmetry plane. Click on the second one down (draft tube face, outside), to select it.

6. Press Apply in the Details View. You should see that the text next to Location now reads 1 2D Region.

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Setting up the Mesh


1. Click on Default Body Spacing in the Tree View, which is contained in Mesh>Spacing. 2. In the Details View, change Maximum Spacing to 1.0 cm, and press Enter on the keyboard to set this value.

A maximum edge length of 1 cm will produce a coarse grid of about 6700 nodes, suitable only for instructional and demonstrative uses. With the use of such a coarse mesh, the recirculation flow patterns in the reactor cannot be resolved adequately and some difficulties in convergence may be expected. To create a mesh that is appropriate for formal quantitative analysis of the airlift reactor in this tutorial, the maximum edge length should be 0.5 cm or shorter. The resulting mesh will contain significantly more nodes.

Because the diameter of the sparger tube is small compared to the dimensions of the reactor, it is desirable to set a


Mesh Generation

Face Spacing on the sparger surfaces to refine the mesh in the vicinity of the sparger.

1. Right-click on Spacing and select Insert>Face Spacing. 2. In the Details View, set Face Spacing Type to Constant, and set the Constant Edge Length to 0.2 cm. 3. Set the Radius of Influence to 0.0 cm, and Expansion Factor to 1.2. 4. For Location, select the two faces which form the sparger (the small hole in the geometry).

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1. Click on Options in the Tree View, and change GTM Filename to BubbleColumnMesh.gtm. 2. Right-click on Mesh in the Tree View and select Generate Volume Mesh.



You can now work through the CFX-5.7 example “Tutorial 16: Gas-Liquid Flow in an Airlift Reactor” using the newly-generated mesh.

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Geometry Creation Home Tutorial 12: Room with Air Conditioning


Tutorial 12: Room with Air Conditioning


This example creates the geometry and mesh for a room geometry, which can then be used in simulations to determine the effectiveness of an air conditioning system. In the CFD simulation, the air is input through a small vent in the roof of the room.

The following geometry and meshing features are illustrated:

● Imprint Surfaces, to add surfaces for boundary conditions; ● Face Spacing, to refine the mesh on a particular face; and ● Inflation.

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Geometry Creation

Geometry Creation



Back To Top

Creating the Solid

The first step is to create the main solid, which is a simple box.

1. Create a new sketch ( ) based on the XYPlane. 2. Use Rectangle from the Draw Toolbox of the Sketching tab to create a rectangle which has one corner at the

origin and another at X = 3.0 m, Y = 3.0 m

3. Select Extrude from the 3D Features Toolbar. 4. Set Base Object to be the new sketch (Sketch1), and set Operation as Add Material.

5. Set Depth to be 2.5 m, and click on Generate to generate the solid.

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Breaking the Faces to form the Boundary Conditions

The solid that you have just created has six rectangular faces. Some of these faces need breaking up, so that the features such as windows, door and vents exist as separate faces of the solid. This can be done by using Extrude with the Imprint Faces option.

Using this option requires sketches of the correct dimensions to be created first. However, when the Extrude operation takes place, you cannot choose to have the Imprint Faces action only apply at a specified face; it will apply at all faces between the sketch and the required face. For this reason, the sketches cannot be created on the existing three planes since then they would always affect the faces of the solids which are co-planar with these planes. This means that you need to start by creating a new plane.

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Geometry Creation

1. Create a new plane ( ), based on the XYPlane. 2. In the Details View, set Transform 1 to Offset Z, and set the Value of the offset to 1 m.


4. Create a new sketch ( ) based on the new plane (Plane4). Use Rectangle from the Draw Toolbox of the Sketching tab to create a rectangle which has one corner at X = 0.05 m, Y = 1.3 m and another at X = 0.15 m, Y = 1.7 m.

5. Select Extrude from the 3D Features Toolbar. 6. Set Base Object to be the new sketch (Sketch2), and set Operation as Imprint Faces.

7. Set Type to be To Next, and click on Generate to break the top face.

Notice that in the figure above, the top face has been selected in order to show that it is in two parts.

These operations now need to be repeated to break the faces to form the windows and side vent.

1. Create a new plane ( ), based on the ZXPlane. [In ANSYS Workbench 8.0.1, create the new plane based on the XZPlane.]

2. In the Details View, set Transform 1 to Offset Global Y, and set the Value of the offset to 1 m.


4. Create a new sketch ( ) based on the new plane (Plane5). Use Rectangle from the Draw Toolbox of the Sketching tab to create a rectangle which has one corner at X = 1.25 m, Z = 0.75 m and another at X = 1.75 m, Z = 1.75 m.

5. Use Rectangle from the Draw Toolbox of the Sketching tab to create another rectangle, which has one corner at X = 2.05 m, Z = 0.15 m and another at X = 2.55 m, Z = 0.55 m.



Geometry Creation

8. Set Direction to Reversed, Type to be To Next, and click on Generate to break a side face. [In ANSYS Workbench 8.0.1, Direction should be set to Normal.]

1. Create a new plane ( ), based on the YZPlane. 2. In the Details View, set Transform 1 to Offset Z, and set the Value of the offset to 1 m.


4. Create a new sketch ( ) based on the new plane (Plane6). Use Rectangle from the Draw Toolbox of the Sketching tab to create a rectangle which has one corner at Y = 1.25 m, Z = 0.75 m and another at Y = 1.75 m, Z = 1.75 m.


7. Set Direction to Reversed and Type to To Next, then click on Generate to break another side face.


Geometry Creation

Finally, you need to break one more face to make a face for the door. However, this time, the plane which contains the sketch to be extruded must be outside the geometry. Otherwise, because the door reaches the edge of the room, you will find that the rectangular (unbroken) face which shares an edge with the door will be broken.

1. Create a new plane ( ), based on the YZPlane. 2. In the Details View, set Transform 1 to Offset Z, and set the Value of the offset to 4 m.


4. Create a new sketch ( ) based on the new plane (Plane4). Use Rectangle from the Draw Toolbox of the Sketching tab to create a rectangle which has one corner at Y = 2.3 m, Z = 0.0 m and another at Y = 3.0 m, Z = 2.0 m.


7. Set Direction to Reversed and Type to To Next, and click on Generate to break the side face.



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Home Mesh Generation


Mesh Generation

Mesh Generation





1. Create a Composite 2D Region called Inlet on the vent in the roof (small rectangular face contained in the plane with the highest Z-coordinate.

2. Create a Composite 2D Region called Roof on the remaining part of the roof (highest Z-coordinate). 3. Create a Composite 2D Region called Window1 on the rectangular face which is cut out from the ZXPlane.

This plane has two cutout rectangular faces, and you need the one which is taller and located at a higher Z-coordinate.

4. Create a Composite 2D Region called Window2 on the rectangular face which is cut out from the YZPlane. 5. Create a Composite 2D Region called VentOut on the rectangular face which is cut out from the ZXPlane.

This plane has two cutout rectangular faces, and you need the one which is smaller and located at a lower Z-coordinate.

6. Create a Composite 2D Region called Floor on the rectangular face which is in the XYPlane. 7. Create a Composite 2D Region called Door on the tall, thin rectangular face which is cut out from the face

with the highest X-coordinate.

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Setting up the Mesh



This is a coarse length scale, suitable only for tutorial purposes. In order to better resolve the flow near the inlet and outlet vents, Face Spacings will be applied to these regions to refine the mesh.

1. Right-click on Spacing and select Insert>Face Spacing.

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Mesh Generation

2. In the Details View, set Face Spacing Type to Constant, and set the Constant Edge Length to 0.04 m. 3. Set the Radius of Influence to 0.0 m, and Expansion Factor to 1.3. 4. For Location, select Inlet from the Tree View. 5. Right-click on Spacing and select Insert>Face Spacing, to create another Face Spacing. 6. In the Details View, set Face Spacing Type to Constant, and set the Constant Edge Length to 0.1 m. 7. Set the Radius of Influence to 0.0 m, and Expansion Factor to 1.3. 8. For Location, select VentOut from the Tree View.

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It is a good idea to put inflation on the walls.

1. Click on Inflation in the Tree View. In the Details View, set Number of Inflated Layers to 5. 2. Set Expansion Factor to 1.2. Leave the rest of the parameters as their default values. 3. In the Tree View, right-click on Inflation and select Insert>Inflated Boundary. 4. For Location, select all of the Composite 2D Regions in the Tree View (including the Default 2D Region)

except for Inlet and VentOut. The Details View should show 6 Composites after you have made the selection.


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1. Click on Options in the Tree View, and change GTM Filename to HVACMesh.gtm. 2. Right-click on Mesh in the Tree View and select Generate Volume Mesh.



You can now work through the CFX-5.7 example “Tutorial 17: Air Conditioning Simulation” using the newly-generated mesh.


Mesh Generation

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Geometry Creation Home Tutorial 13: Can Combustor


Tutorial 13: Can Combustor


This example creates the mesh for a can combustor, which might typically be found in a gas turbine engine. The geometry is complex and consists of 5 separate solid bodies. It will be imported complete from a Parasolid file. The diagram above right shows the geometry schematically with part of the outer wall cut away. The following geometry and meshing features are illustrated:

● Parasolid import; and ● Inflation.

This tutorial requires you to have a copy of the Parasolid file Combustor.x_t. If you do not already have this file, then download it here (you will need to execute the downloaded file to extract the Parasolid file).

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http://www.ansys.com/dm_how_tos/cm_combustor.exe


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Mesh Generation Home Geometry Import

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Geometry Import

Geometry Import



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Importing the Geometry

The geometry is imported complete from a Parasolid file.

1. Select File>Import External Geometry File... from the Menu Toolbar. 2. In the file browser which opens, locate the file Combustor.x_t and choose to Open it. (If you have not

already got this file, refer to the introduction to this tutorial for details of where to find it.)

3. Click on Generate to import the combustor.

The Tree View should now show that you have 5 Parts, 5 Bodies. In order to produce a single mesh on the bodies, they must be combined into one part.

1. From the Selection Toolbar at the top of the window, turn on Select Bodies ( ). This means that you can only select Solid Bodies in the next operation, which helps to make the selection process easier.

2. In the Model View, select all 5 bodies as follows:

● Click on Select Mode ( ) and choose Box Select from the drop-down menu. ● Whilst holding down the left mouse button, drag a box across the whole geometry to select all 5

bodies. Once you have released the mouse button, the status bar (the bar along the bottom of the ANSYS Workbench window) should change to show that you have selected 5 Bodies.

3. Right-click over the Model View and select Form New Part.

The Tree View should now show that you have 1 Part, 5 Bodies. The geometry does not need any further modifications.


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Geometry Import

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Tutorial 13: Can Combustor Home Mesh Generation

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Mesh Generation

Mesh Generation





1. Create a Composite 2D Region for the fuel inlet called fuelin on the six tiny faces on the cone near the bottom of the combustor. The easiest way to select them as follows:

a. Click over the axes in the bottom right corner of the Model View in the position shown in the picture below. As you move the cursor into this position, the black “-Z”-axis will appear (it is not shown by default). This will put the geometry into a good position for picking the required faces.

b. Zoom into the geometry and select the six faces which are shown in bright green in the picture below (note that the colors in your geometry may differ from the picture below).

2. Create a Composite 2D Region for the air inlet called airin on the eight faces at the very bottom of the geometry (lowest Z-coordinate), as shown below.

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Contents•CopyrightTutorial 13: Can Combustor> Mesh Generation

Mesh Generation

3. Create a Composite 2D Region for the secondary air inlet called secairin on the six small circular faces on the main body of the combustor. These introduce extra air to aid combustion.

4. Create a Composite 2D Region called out on the rectangular face with the highest Z-coordinate.

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Setting up the Mesh

This is a complex geometry which will be used to run a simulation with complex physics. In order to keep the computational time down for the purposes of the tutorial, a very coarse mesh will be used. If you wanted to get accurate results on this geometry, a much finer mesh and a much larger solution time would be required.


1. Click on Default Body Spacing in the Tree View, which is contained in Mesh>Spacing. 2. In the Details View, change Maximum Spacing to 1.6 cm, and press Enter on the keyboard to set this value. 3. Click on Default Face Spacing in the Tree View, which is contained in Mesh>Spacing. 4. In the Details View, change Face Spacing Type to Volume Spacing.

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Mesh Generation

It is a good idea to put inflation on the walls.

1. Click on Inflation in the Tree View. In the Details View, set Number of Inflated Layers to 5. 2. Set Expansion Factor to 1.3. Leave the rest of the parameters as their default values. 3. In the Tree View, right-click on Inflation and select Insert>Inflated Boundary. 4. For Location, select Default 2D Region from the Tree View. 5. Set Maximum Thickness to 1.6 cm.

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You can now generate the volume mesh.

1. Click on Options in the Tree View, and change GTM Filename to CombustorMesh.gtm. 2. Right-click on Mesh in the Tree View and select Generate Volume Mesh.

The mesh is now complete. Note that you may get a warning about poor quality volume elements being present in the mesh. This is a result of setting up such a coarse mesh. If you wanted to get accurate results in the CFD simulation, you would need to modify the mesh settings and regenerate the volume mesh in order to improve the quality of the elements.


You can now work through the CFX-5.7 example “Tutorial 18: Combustion and Radiation in a Can Combustor” using the newly-generated mesh.

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