fluent gambit

7/30/2019 fluent gambit

1/39

Fluent Inc. 12/28/20122-1

Fluent User Services Center

www.fluentusers.com

Introductory GAMBIT Notes

GAMBIT v2.1 Jul 2003

Creating Geometry in GAMBIT


2/39

Fluent Inc. 12/28/20122-2


www.fluentusers.com



Preliminaries-1

Objective:

Create and mesh the fluid region for flow problems and solid

regions for heat transfer (and structural analysis for Fidap Users).

Typically accomplished by constructing and working with lower

order entity objects and volume primitives. Terminology:

Vertex - a point

Edge - a curve that is defined by at least 1 vertex (in the case of 1

vertex, the edge forms a loop)

Face - a surface (not necessarily planar) bounded by at least 1 edge(except for sphere and torus)

Volume - a geometric solid (as in a solids model), also can be

thought of as an "air tight" set of bounding faces.

Lowest order entity

Highest order entity


3/39

Fluent Inc. 12/28/20122-3


www.fluentusers.com



Preliminaries-2 Color Identification

Vertices and Edges are colored according to the highestorder entity to which they are connected.

The coloring scheme is:

Vertex (white)

Edge (yellow)

Face (light blue)

Volume (green)

Undo/Redo:

10 levels of undo by default.

Undoes geometry, meshing, and zoning commands.

Description window provides command to be undonewhen mouse is passed over undo button.

Left click to execute visible button operation.

Right click to access options.


4/39

Fluent Inc. 12/28/20122-4


www.fluentusers.com



General Operations: Coordinate System

Coordinate system

Cartesian, Cylindrical and Spherical systems

Using Offset/Angle or Vertices for location/orientation

"Active" coordinate system is default in all formsGrid creation with "snapping" of vertices

-Recommended for simple geometries only

Creation of rulers


5/39

Fluent Inc. 12/28/20122-5


www.fluentusers.com



General Operations: Move/Copy

Move/Copy

Operations:

Translate:

(inputs are Ds)

Reflect:

Plane normal to

vector

(x,y,z)

Angle

Vector

Vector

Rotate:

Scale:

Options:

Connected geometry can also be Moved

Mesh and/or Zone types can be copied linked or unlinked


6/39

Fluent Inc. 12/28/20122-6


www.fluentusers.com



General Operations: Vector Definition Form

Vector Definition form

is used in:

Rotate and Reflect (in Move/Copy)

Sweep and Revolve (in Face/Volume

Create)

Methods:

Coordinate system axis

Two existing vertices

An existing Edge

Two points defined by coordinates

Screen View

Magnitude option allows size of vector

to be defined.


7/39 Fluent Inc. 12/28/20122-7


www.fluentusers.com



General Operations: Align

Align

Align is an alternative to

Move - translate (+rotate).

It uses vertices on the start and

final position to move the object

Method of increased alignment

with the use of vertex-pairs

Connected geometry can be included

Rotation Plane alignmentTranslation++

++ ++++ + +

3 3

1 1

2 2


8/39 Fluent Inc. 12/28/20122-8


www.fluentusers.com



General Operations: Connect

Connect (Real)

Vertices, Edges and Faces can be connected

The operation eliminates all duplicate entities

and reconnects upper topology Only entities within the ACIS tolerance

will be connected

Existing mesh will be preserved

Connect EdgesCopy +Translate

Two Edges One EdgeOne Face


9/39 Fluent Inc. 12/28/20122-9


www.fluentusers.com



General Operations: Disconnect

Disconnect (Real)

Vertices, Edges and Faces can be

disconnected

The operation recreates duplicate entities

and reconnects upper topology

Several options exists

Disconnect

Two EdgesOne EdgeEdge + Vertices


10/39 Fluent Inc. 12/28/20122-10


www.fluentusers.com



General Operations: Delete

Delete

Select Lower Geometry(default)

Deletes Faces

Deletes Lower Geometry:Edges and Vertices

Deselect Lower Geometry

Deletes Faces

Does NOT delete LowerGeometry: Edges andVertices


11/39 Fluent Inc. 12/28/20122-11


www.fluentusers.com



Example: Deleting Entities that belong to

higher order Entities

The selected face can NOT be deleted

because it is connected to a volume.

Correct: Delete Volume

(deselect Lower Geometry)

Volume is deleted. Faces, Edges and Vertices are

not deleted. Any of the six faces can be deleted

Incorrect: Attempt to delete

Face (of a Volume)


12/39 Fluent Inc. 12/28/20122-12


www.fluentusers.com



General Operations: Misc.

Summarize/Query/Total

Summary of vertex coordinates,lower topology, mesh information,

element/node labels, etc.

Checks for valid ACIS geometry

Query: useful to associate geometrical objects with object namesGet total number of Entities

Modify Color/Label

Modify entity colors

Change entity label


13/39 Fluent Inc. 12/28/20122-13


www.fluentusers.com



Geometry Creation

ACIS - geometry engine ("kernel")

Provides tools for bottom-up creation by:

Vertex: Add, Grid Snap, etc.

Edge: Line, Arc, Ellipse, Fillet, B-spline, etc.

Face: Wire Frame, Sweep, Net, etc.

Volume: Wire Frame, Sweep, Face Stitch, etc.

Provides tools for top-down creation by

Face Primitives: Rectangle, Circle, Ellipse

Volume Primitives: Brick, Cylinder, Sphere, etc.

Volume/Face Booleans: Unite, Subtract, Intersect

Volume/Face Decompose: Split

Geometry creation typically involves use of all tools.


14/39 Fluent Inc. 12/28/20122-14


www.fluentusers.com



"Bottom Up": Vertex Creation-1

Real Vertex creation

By coordinates

Cartesian, cylindrical and spherical coordinate systems

Also available in virtual geometry

On edge

If the intention is to split the edge, the Edge-Split

form should be used instead

On face

Useful to create edges on surface for a virtual split

In volumes

Not frequently used

At edge-edge intersections

Vertex is not connected to either edge

Split edge with vertex for connectivity


15/39 Fluent Inc. 12/28/20122-15


www.fluentusers.com



"Bottom Up": Vertex Creation-2

Import point data, File

File format:

ICEM Input

Vertex Data

Format is similar, curve information is not needed

npc nc

x1 y1 z1

x2 y2 z2

:

xn yn zn

Where: n = npc* nc is the total number of points

npc

is the number of points per curve

nc is the number of curves

xi yi zi are real or integer vertex coordinates


16/39 Fluent Inc. 12/28/20122-16


www.fluentusers.com



"Bottom Up": Edge Creation-1 Real Edge creation

Straight line

Multiple edges can be created by selecting

multiple vertices.

Arc, Circle

Face create counterparts available Creation Methods

Three vertices on the edge

Using Center and End-points

Using Radius and Start/End Angles (Arc

Only)


17/39 Fluent Inc. 12/28/20122-17


www.fluentusers.com



"Bottom Up": Edge Creation-2

Real Edge creationElliptical Arc

Created by three vertices

Conic Arc

Created by three vertices

+

+

+Major Vertex

On Edge VertexCenter VertexEnd Angle

Start Angle

+

+

+Shoulder Vertex

End Vertex

Start Vertex


18/39 Fluent Inc. 12/28/20122-18


www.fluentusers.com



"Bottom Up": Edge Creation-3 Real Edge creation

Fillet Arc

Creates a fillet out of a corner

NURBS

Third-order by default

Use tolerance for the approximate option

+

++Edge 1

Edge 2

Radius


19/39 Fluent Inc. 12/28/20122-19


www.fluentusers.com



"Bottom Up": Edge Creation-4

Real Edge creation

Revolve Vertex

Select one or more vertices to rotate

Specify Angle

Axis is defined using Vector Definition Panel

Input Height for Spiral creation

Project Edge on Surface

Limited to single edge

and face

Direction defined in

Vector Definition

Panel


20/39

Fluent Inc. 12/28/20122-20


www.fluentusers.com



"Bottom Up": Face Creation-1 Real Face creation

Wire Frame

Creates real and virtual faces

All edges have to be connected into one loop

Number of edges and order of picking are not important

If all edges are co-planarcreation is always successful For non-coplanar edges:

The number of edges has to be 3 or 4

Edges cannot have the same tangent

at the connecting vertex

create real face

by wire frame

co-planar edges real face

+


21/39

Fluent Inc. 12/28/20122-21


www.fluentusers.com



"Bottom Up": Face Creation-2

Real Face creation

Parallelogram

defined by three vertices

Polygon

Selection order is important.

5 or more vertices must be coplanar.

Vertex rows

Tolerance input

Skin

Topologically parallel edges

Edges have to be picked in order

Both ends of all edges can coincide

Net

Topologically intersecting edges

+

+

+

++

+

+

+

+

+

+

++

+

+

+

+

+

+

+

+ +

+

+

+

+

+

+

++

+

+


22/39

Fluent Inc. 12/28/20122-22


www.fluentusers.com



"Bottom Up": Face Creation with Revolve Real Face creation

Revolve (With or without mesh)

Using an edge, an angle and a

revolving vector

Use vectors for definition of the axis

of revolution Basic edge can coincide with axis

axis of revolution


23/39

Fluent Inc. 12/28/20122-23


www.fluentusers.com



"Bottom Up": Face Creation with Sweep

Path

Perpendicular Twist:

Angle = 120

Perpendicular Draft:

Angle = - 30, 0, 30

Rigid

Path

Edge

Real Face Creation: Sweep (with or without mesh)

Rigid sweep

Edge translated along sweep path without being rotated

Perpendicular sweep: Draft and Twist option

Angle edge makes with sweep path is maintained as edge

swept along path

Be careful not to create degenerate faces

Sweep path start tangent vector parallel to edge tangent

Edge

RigidPerpendicular

Draft: Angle=0


24/39

Fluent Inc. 12/28/20122-24


www.fluentusers.com



Face Primitives

Face Primitives

Dimensions and Plane/Direction must be specified

Rectangles

Circles

Ellipses


25/39

Fluent Inc. 12/28/20122-25


www.fluentusers.com



"Bottom Up": Volume Creation-1

Real Volume creation

Stitch

Create volumes out of connected faces

If a few faces are missing, GAMBIT

automatically finds the missing

faces

Available in virtual geometry

Order of picking not essential

Voids not allowed

Revolve (With or without mesh) Using a face, a revolving vector and an

angle

Use edges or vectors for definition of

the axis of revolution

ten connected faces one volume

axis of revolution


26/39

Fluent Inc. 12/28/20122-26


www.fluentusers.com



"Bottom Up": Volume Creation-2

Real Volume creation

Wire Frame

Create volumes from connected curves

Number of edges and order of picking is not important

Voids and seamless volumes and faces cannot be created

Same limitation as face wire frame creation, for each face

36 connected edges one volume


27/39

Fluent Inc. 12/28/20122-27


www.fluentusers.com



"Bottom Up": Volume Creation with Sweep

Path

Perpendicular Twist:

Angle = 60Rigid

Real Volume Creation: Sweep (with or without mesh)

Rigid sweep

Edge translated along sweep path without being rotated

Perpendicular sweep: Draft and Twist option

Angle edge makes with sweep path is maintained as edge swept

along path

Be careful not to create degenerate volumes

Sweep path start tangent vector perpendicular to a face normal

Path

Face

Perpendicular

Draft: Angle=0

Face


28/39

Fluent Inc. 12/28/20122-28


www.fluentusers.com



Volume Primitives-1

Real Volume Primitives

Brick

Width (X), Depth (Y) and Height (Z)

The Width (X) value is used for Y and Z if

no other input is given. 10 different preset positions (each octant plus

center)

Cylinder and Frustum

Height and two cross-sectional radii (3rd

radius for frustum)

The Radius 1 value is used for remaining

radii if no other radius input is given.

9 different preset directions (three in each

axis)


29/39

Fluent Inc. 12/28/20122-29


www.fluentusers.com



Volume Primitives-2

Real Volume PrimitivesPrism and Pyramid

Corresponding to input of cylinder and

frustum

Number of sides

9 different preset directions (three in each

axis)

Sphere - only one radius

Torus

Major and cross-sectional radii

Three axis locations

d GAMBIT


30/39

Fluent Inc. 12/28/20122-30


www.fluentusers.com



Boolean Operations: Unite

Real Face/Volume Boolean Unites The order of picking is not important (except for labeling)

Retain - keeps copies of the entities

Unite Faces

All faces must be coplanar or have

matching tangents.

Unite Volumes

AB A + B

AB A + B

Fl U S i C I d GAMBIT N


31/39

Fluent Inc. 12/28/20122-31


www.fluentusers.com



Boolean Operations: Subtract

Real Face/Volume Boolean Subtract

The order of picking is important

Retain - keeps copies of entities

Subtract Faces

All faces have to be coplanar

Subtract Volumes

AB A - B

B - A

A - B B - A

A

B

A

B

Multiple entities can be entered

in second list box.

Fl t U S i C t I t d t GAMBIT N t


32/39

Fluent Inc. 12/28/20122-32


www.fluentusers.com



Boolean Operations: Intersection

Real Face/Volume Boolean Intersect

The order of picking is not important (except for labeling)

Retain - keeps copies of entities.

All entities must intersect each other.

Intersect Faces

All faces have to be coplanar

Intersect Volumes

BA

B

A

Fl t U S i C t I t d t GAMBIT N t


33/39

Fluent Inc. 12/28/20122-33


www.fluentusers.com



The Split Operation: Employs the intersection of two geometric entitiesto divide one or both objects into two or more pieces.

Useful for decomposing complicated geometries into smaller, simpler ones.

Edge Split

Split an edge into two or more edges

Resulting edges are, by default, connected.

Edges can be split with:

Point - specify U Value between 0 and 1

where edge will be split.

Use 0.5 to split edge in half.

Vertex - must already be created. Edge

Must already be created

Bi-directional option results in both edges

being split at point(s) of intersection.

Geometry Splitting- Edges

Fl t U S i C t Introductory GAMBIT Notes


34/39

Fluent Inc. 12/28/20122-34


www.fluentusers.com



Geometry Splitting- Faces

Real Face Boolean Split The order of picking is important

Faces do not need to be coplanar

example: coplanar face splits

In general, for all splits (edges, faces, volumes): "Tool" entities are, by default, deleted after split is

performed

Retainoption prevents Tool entities from beingdeleted.

By default, resulting objects are connected.

Split A

with B

Split B

with A

Two Faces

"Target Object"

"Tool"

Bidirectional

split

Three Faces

Fluent User Services Center Introductory GAMBIT Notes


35/39

Fluent Inc. 12/28/20122-35


www.fluentusers.com



Geometry Splitting- Volumes

Real Volume Boolean Split

The order of picking is important

Volume/Volume splits

two volumes

Bidirectional

Split

three volumes

Split Awith B

B

A

two volumes

Split B

with A

two volumes Volume/Face splits

"Target" Object

"Tool"

B

A

B

A



36/39

Fluent Inc. 12/28/20122-36


www.fluentusers.com



The appropriate operation to use candepend upon final geometry required.

Subtract

Cut-away shows one volume results

Cannot mesh core region

Flow/Heat Transfer in annular region only Split

Two connected volumes result

Cut-away shows that both annular and core

regions can be meshed.

Flow/Heat Transfer possible in both regions

Subtract + Retain "Tool" (inner cylinder)

Two disconnected volumes result, appears same as split

Duplicate faces appear at interface

Non-conformal mesh can result

Useful for multiple reference frame problem (Fluent)

Split vs. Subtract

Start with two

disconnected

cylinders



37/39

Fluent Inc. 12/28/20122-37


www.fluentusers.com



The appropriate operation to use candepend upon the need to create

additional surfaces for:

defining boundary conditions

controlling meshing distribution

Bidirectional Split vs. Unite

Unite

Unite One volume results

Cut-away shows no

interior faces

BiDirectional

Split

Bidirectional split

Three connected volumes result

Cut-away shows multiple interior faces which can be used to:

define internal boundaries

help control mesh distribution in volume

Total represented volume is the same

Start

with two

disconnected cylinders



38/39

Fluent Inc. 12/28/20122-38


www.fluentusers.com



Boolean Characteristics: Imprinting Uniting Connected Volumes Results in Imprinting

Unite A

with B

A and C are connected cubes, B is

a cylinder inside both

A C

Volume.1

Volume.2: face contains an

imprint of the cylinder

B



39/39


www.fluentusers.com



Volume Blends Real Volume Blends

Blend - create fillet/rounded edges

Pick a volume

Pick the edges that need a blend and

specify radius

Pick vertex (if needed) and specify radiususing the Setback option

Bulge option is not recommended for

hexahedral meshing

Bulge option

Setback option

Documents

fluent gambit