PRELUDE New PHOENICS pre-processor

1. 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.

2. 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.

3. 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

4. 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 Satellite Solver eardat & facetdat q1 q3 • Satellite then converts the data into eardat and facetdat and passes them to the solver. • PRELUDE also saves its work in a Q3.

5. 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.

6. Main featuresof PRELUDE, 2 • 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?

7. 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'.

8. Relationships exemplified

9. 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.

10. 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.

11. 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.

12. 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 thatthey need, but no more. • They are not required to make CFD-specific decisions.

13. 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.

14. 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.

15. 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’.

16. 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

17. 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.

18. 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)

19. 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.

20. Parametric Baffle • Adjusting the parameters such as ‘cutout’ and ‘length’; • changes the shape without editing and saving a geometry file.

21. ‘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.

22. 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.

23. 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.

24. 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.

25. 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.

26. 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.

27. 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.

28. 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.

29. The liquid-ring-pump gateway One of the first gateways concerned the two-phase pump shown here. A free surface has to be computed between rotating water and air. Air pressure, temperature and humidity all vary greatly.

30. More about the liquid ring pump This still picture shows a little more detail

31. More about the liquid ring pump As does this also

32. More about the liquid ring pump The phenomenon is transient but becomes cyclic. Many time steps must be computed

33. More about the liquid ring pump more detail

34. More about the liquid ring pump The torque is of interest to the designers

35. 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 particulartopics or phenomena. • Its relational capabilities are its main merits.

36. 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.