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PRELUDENew PHOENICS pre-processor

• Why does PHOENICS need a new pre-processor?

• In the first years of PHOENICS, data were input via text files (Q1s) written in PIL (PHOENICS Input Language).

• PIL had (and has) many valuable features: (declaration of new variables, logic, DO loops, CASE structures, file reading, etc; but not all users found it easy.

• For these users, the VR-Editor was introduced, which wrote Q1s for them.

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What the VR-Editor could and could not do

• The VR-Editor had many merits, e.g.-- visual display and manipulation;-- attention focussed on objects.-- use of x, y, z, rather than ix, iy, iz .

* However the Editor was not able to handle some important PIL features, such as:

-- declarations,-- logic,-- expressions,-- DO loops,-- case structures, and-- (at first) In-Form statements.

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Resulting shortcomings,and their removal

• Consequently the Q1 written by the VR-editor defines adequately the data needed for a single solver run.

• However, it loses any declarations, etc which were present in the Q1 form which it started.

• It therefore contains no record of the class of runs of which its written Q1 launches a single instance.

• PRELUDE has been introduced as a means of preserving and enriching that record.

• PRELUDE looks (and acts) the same under both Windows and Unix/Linux, because it is written in the Tcl/Tk language. and

• It also employs the OpenSceneGraph graphics engine

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Relation of PRELUDE to Satellite and Solver

• PRELUDE and Satellite work in tandem. • PRELUDE passes its output data to

Satellite in the form of a Q1 file, which• the VR-Editor may modify if the user so

wishes; but this is rarely necessary.

Prelude q1 Satelliteeardat &facetdat

Solver

• Satellite then converts the data into eardat and facetdat and passes them to the solver. • PRELUDE also saves its work in a Q3.

q3

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Main featuresof PRELUDE, 1

PRELUDE processes input data provided by one or more of the following:

• a single-instance Q1 file, • a multiple-instance Q3 file, • a script containing human-editable commands, • input, especially of data relationships, provided

interactively by the user, • .dat files defining shapes, • .ac files created by AC3D, • .stl files, • .pob files.

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• PRELUDE allows relationships to be typed into boxes, whereafter they are acted upon instantly.

• This is probably the most important of all the features of PRELUDE.

• Its relational character distinguishes it from Satellite in the same way as an EXCEL spread-sheet is distinguished from a mere calculator.

• Does any competing code possess this?

Main featuresof PRELUDE, 2

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Further features

• PRELUDE can launch a series of PHOENICS runs, with different values of specified parameters, and access the results in an orderly way.

• PRELUDE treats 'phi-variables' as objects having attributes, in a manner similar to physical objects (except that they have no visual representation).

• PRELUDE also treats as objects 'models' such as IMMERSOL, k-epsilon, and solid-stress, which appear on the 'object-tree as children of the 'domain' object and as parents of their associated 'phis'.

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Relationships exemplified

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Main features, 3

• PRELUDE can record the results of an interactive-input session in the form of a Q3 file, which, because it preserves the algebraically-expressed relationships between the data elements, can be used for the creation of an unlimited number of individual-instance simulations.

• PRELUDE has 'undo' capabilities.• Prelude provides ‘Gateways’ to PHOENICS

which ‘customises it for special-sector users.

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What is a Q3?

• A Q3 is a kind of generalised Q1, embodying classes of cases, not just single instances.

• It preserves declared variables.• It preserves relationships.• Although often created and modified

interactively, it is human-editable.

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What is a Gateway?

A Gateway consists of: • a script which sets up an initial scenario; • a 'store-cupboard' containing a set of objects with

attributes which the user is is expected to need ; • An html file embodying a tutorial which enables the

new user to learn what to do; • some exemplary Q3s.

Examples are: • Beginners, for learning about PRELUDE, • Virtual Wind Tunnel, for forces on objects,• FLAIR, for HVAC and smoke movement.• LRP, for liquid-ring pumps.

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Who will use PRELUDE ? 1

• Users of the Gateway approach to PHOENICS.

• Gateways allow users to perform simulations of pre-defined kinds, with the minimum of difficulty.

• Such users are presented with all that they need, but no more.

• They are not required to make CFD-specific decisions.

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Who will use PRELUDE ? 2

• The makers of Gateways

-- consultants, for their clients,

-- lecturers, for their students,

-- CHAM staff, for selected application sectors,

-- the customers/ PHOENICS experts, for their ‘coal-face’ colleagues.

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What is a PRELUDE script?

• A PRELUDE script is a file, written in Tcl/Tk with extensions introduced by CHAM, which tell PRELUDE what to do.

• It acts like a ‘macro’ of PRELUDE-user key-board entries.

• It is NOT for the general user (either ‘forward’ or ‘mid-field’); but CHAM could offer training in script-writing.

PRELUDE

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More about Gateways

• Gateways are much easier to create than special-purpose programs.

• Three which are now being finalised are:-- The Virtual Wind Tunnel-- Heating, Ventilating and Air-conditioning-- Fire, and smoke movement.

• A recent development for a client was for a ‘liquid-ring pump’.

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In-Form Boundary Conditions

• Inlet conditions can be specified as functions of coordinates and other parameters, e.g.

• parabolic velocity at inlet with a single-inlet object

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In-Form in PRELUDE

• Prelude defines the In-Form statements as text.

• EARTH interprets the statements.

• Prelude saves and restores the statements and can add new statements.

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Formats other than .dat

• Numerous file formats are supported by the OpenSceneGraph graphics engine embodied in PRELUDE;

• Here for example is a 3DSmodel of a watch with texture)

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Parametric Objects

• These are defined by Tcl scripts, created by the user or a consultant).

• Example: a baffle with a cut-out area. Shape parameters are radius, cut-out depth, length and number of facets.

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Parametric Baffle

• Adjusting the parameters such as ‘cutout’ and ‘length’;

• changes the shape without editing and saving a geometry file.

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‘Tree’ representation of Scene

• A ‘Scenegraph’ is used to optimise performance and achieve hierarchical graphics.

• The table, plus chair and computer constitute a single assembly; but PHOENICS can set separate properties for each component.

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Hierarchical Table

• Rotate the assembly (table); then all the other parts remain at the same relative positions.

• Position in PHOENICS is handled automatically by PRELUDE.

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Textured Objects

• PRELUDE can use AC3D to generate textured objects; or

• other data sources. Here is an OSG (i.e. Open Scene Graph representation of a cow.

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Using other objects

The cow is passed, as a VR object, to the PHOENICS solver, EARTH.

Then the flow around the cow, in a virtual wind-tunnel, is computed.

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Architecture

• Very complex models can be imported into PRELUDE; and can then be exported to EARTH.

• PARSOL does its best to fit.

• In this case there are 46982 vertices, and

• 23208 facets.

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Results of flow around the house

• This was very hard to mesh because of open windows;

• but PARSOL gives this result in less than 4 minutes on a 2GHz PC.

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Multiple runs

• PRELUDE can perform multiple runs, varying a parameter on each run.

• Here an airfoil is placed in the VWT (Virtual Wind Tunnel); and its incidence is changed from -15 to 5 degrees with 5-degree interval.

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Influence of Incidence angle

After about 5 minutes, there resulted the 5 runs displayed here (with incidence = -15, -10, -5, 0, +5 degrees).

The scales of pressure are not identical in the examples.

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The liquid-ring-pump gateway

One of the first gateways concerned the two-phase two-phase pumppump shown here.

A free surface has to be computed between rotating water and air.

Air pressure, temperature and humidity all vary greatly.

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More about the liquid ring pump

This still picture shows a little more detail

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More about the liquid ring pump

As does this also

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More about the liquid ring pump

The phenomenon is transient but becomes cyclic.

Many time steps must be computed

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More about the liquid ring pump

more detail

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More about the liquid ring pump

The torque is of interest to the designers

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Summary

• PRELUDE is a tool for focussing attention on selected PHOENICS features.

• Consultants can produce special- purpose ‘gateways’ to enable clients to utilise easily the features which they have delivered.

• Professors, and their students, can use it to facilitating teaching and study of particular topics or phenomena.

• Its relational capabilities are its main merits.

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The future of PRELUDE

• Add a rigid-body-dynamics code to provide inputs to MOFOR.

• Improve access to DWG, DXF and other CAD formats.

• Display results in the PRELUDE graphics scene.

• Plus facilitate input to Unstructured PHOENICS.

• Accept and process via PHOENICS data prepared for another code, e.g. CFDesign.or HTRI’s Xist.