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PRELUDE
PH
OE
NIC
S U
ser
Mee
tin
gs
2008
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.
PRELUDE
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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.
PRELUDE
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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
PRELUDE
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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
PRELUDE
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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.
PRELUDE
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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
PRELUDE
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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'.
PRELUDE
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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.
PRELUDE
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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.
PRELUDE
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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.
PRELUDE
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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.
PRELUDE
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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.
PRELUDE
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2008
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’.
PRELUDE
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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
PRELUDE
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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.
PRELUDE
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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)
PRELUDE
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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.
PRELUDE
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Parametric Baffle
• Adjusting the parameters such as ‘cutout’ and ‘length’;
• changes the shape without editing and saving a geometry file.
PRELUDE
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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.
PRELUDE
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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.
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.
PRELUDE
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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.
PRELUDE
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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.
PRELUDE
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2008
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.
PRELUDE
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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.
PRELUDE
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2008
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.
PRELUDE
PH
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2008
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.
PRELUDE
PH
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Mee
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2008
More about the liquid ring pump
This still picture shows a little more detail
PRELUDE
PH
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Mee
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2008
More about the liquid ring pump
The phenomenon is transient but becomes cyclic.
Many time steps must be computed
PRELUDE
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2008
More about the liquid ring pump
The torque is of interest to the designers
PRELUDE
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2008
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.
PRELUDE
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2008
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.
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