PHOENICS/FLAIR for the Wind Environmental Simulation 2008 by Jeremy Wu

1. Computer Simulation of Fluid Flow, Heat Flow, Chemical Reactions and Stress in Solids. PHOENICS/FLAIR for the Wind Environmental Simulation 2008 by Jeremy Wu

2. PHOENICS Overview P arabolic H yperbolic O r E lliptic N umerical I ntegration C ode S eries • PHOENICS is a general-purpose CFD code • The name PHOENICS is an acronym standing for:

3. PHOENICS Overview • PHOENICS is based on the finite volume method. • Domain is discretized into a finite set of control volumes or cells. • General conservation (transport) equation for mass, momentum, energy, etc., unsteady convection diffusion source are discretizedinto algebraic equations as follows:

4. Discretize the equations in conservation (integral) form For the conservation equation for variable f, the following steps are taken: • Integration of conservation equation in each cell. • Calculation of face values in terms of cell-centered values. • Collection of like terms. Finally

5. Main Features of PHOENICS • 1-,2- and 3-D geometries • Relational input capability • Cartesian, Polar and Body-Fitted Coordinates • Local multi-level fine-grid embedding • Cut-cell technique for complex geometry • Conjugate Heat Transfer • Single or Multi-Phase Flow • Particle Tracking • Chemical reaction • Radiation • Non-Newtonian Flow • Choice of equation solvers and differencing schemes • Automatic generation of user code • Automatic convergence control

6. PHOENICS predicts quantitatively:- how fluids (air, water, steam, oil, blood, etc) flow in and around: engines, process equipment, buildings, lakes, river and oceans, and so on; the associated changes of chemical and physical composition; Main Features of PHOENICS

7. PHOENICS consists of several modules: Pre-processor for setting up problems, Solver for solving the problem, Post-processor for visualising results; and POLIS for providing information. PHOENICS Structure

8. PHOENICS Structure POLIS Information

9. How the problem is defined Problem definition normally involves making statements about: • geometry, ie shapes, sizes and positions of objects and intervening spaces; and grid, ie the manner and fineness of the sub-division of space and time; • processes, for example:- whether the heat transfer is to be calculated; whether materials are inert or reactive; whether turbulence is to be simulated and if so by what model;

10. How the problem is defined • materials, ie thermodynamic, transport and other properties of the fluids and solids involved; • Environmental or boundary conditions; and • other numerical (ie non-physical) parameters affecting the speed, accuracy and economy of the simulation.

11. The Virtual-Reality Interface Model setup – VR Editor • Clicking on an object brings a dialogue box onto the screen. • This enables the information about the object to be edited.

12. The Virtual-Reality InterfaceImport a CAD file Model setup – VR Editor • The object geometry can be taken from a library of shapes, or loaded from a CAD file. • CAD geometries are read using the STL format

13. Setting Up Problems: PHOENICS-VR main menu • The PHOENICS-VR Main menu allows you to make all the settings required for a problem, including: • Geometry • Variables to be solved (models) • Fluid properties • Initial values • Boundary • conditions • Monitoring • options

14. A Typical EARTH Convergence Monitor Plot • EARTH is the program that performs the simulation. • The graphical monitor shows the converging solution.

15. Solver-Graphics Monitoring • The EARTH run can be interrupted to change several parameters: • Monitoring position • Relaxation factors • Graphical monitor settings • Intermediate result files can also be dumped

16. Analysis of Results - VR Viewer The VR Viewer allows users to see their results in a number of different ways:

17. Analysis of Results - VR Viewer Streamlines, static or animated Iso-surfaces Contours Vectors

18. AUTOPLOT X-Y graphs plot This allows for easy comparison of PHOENICS solutions with experimental or analytical data.

19. Programmability • Users' subroutine, GROUND • PLANT converts user-defined formulae into error-free Fortran coding and places it correctly in GROUND • In-Form carries the PLANT idea one stage further, by: • eliminating the Fortran writing, • eliminating the compilation, • eliminating the executable-building, • simplifying the syntax, and • enlarging the functionality.

20. What is FLAIR? • FLAIR is a Special-Purpose version of the general CFD code PHOENICS. • It has been created by removing many unneeded generic features, and adding several specific features. • FLAIR is designed to provide an air-flow and thermal-simulation facility for the HVAC community, and for those concerned with the performance of airflow systems for the built environment, and with fire, smoke and pollutant hazards for both internal and external flow scenarios.

21. What does FLAIR do ? • FLAIR predicts air-flow patterns, temperature distributions and smoke movement in buildings and other enclosed spaces. • FLAIR can be used during the design process to detect and avoid uncomfortable air speeds or temperature. • FLAIR also predicts effects of smoke movement, or any other gaseous pollutant, helping to achieve safe design of buildings, underground systems, aircraft or train cabins etc.

22. FLAIR Features • FLAIR uses the PHOENICS VR-Editor to set the problem up, with the following additional items: • ISO 7730 Comfort index calculations: PMV, PPD. • ISO 7730 Draught rating. • CIBSE dry resultant temperature. • Humidity calculations, with output of humidity ratio and relative humidity. • Smoke movement calculation, with output of PPM, smoke density and visibility. • Mean age of air calculation. • Fan operating point calculation for single and multiple fans. • System-curve calculations.

23. FLAIR Features • In addition, the following object types have been added: • Diffuser Round

24. Round diffuser

25. FLAIR Features • In addition, the following object types have been added: • Diffuser Vortex

26. Vortex diffuser

27. FLAIR Features • In addition, the following object types have been added: • Diffuser Rectangular

28. Rectangular diffuser

29. FLAIR Features • In addition, the following object types have been added: • Diffuser Directional

30. Directional diffuser

31. FLAIR Features • In addition, the following object types have been added: • Diffuser Grille

32. Grille/Nozzle

33. FLAIR Features • In addition, the following object types have been added: • Diffuser Displacement

34. Displacement diffuser

35. FLAIR Features • In addition, the following object types have been added: • Diffuser • Fire

36. FLAIR Features • In addition, the following object types have been added: • Diffuser • Fire • Person (standing or sitting • facing any Direction)

38. FLAIR Features • In addition, the following object types have been added: • Diffuser • Fire • Person • Crowd • Sunlight • Created in • Shapemaker

39. FLAIR Features • In addition, the following object types have been added: • Diffuser • Fire • Person • Crowd • Sunlight • Spray head

40. FLAIR Features • Spray-head represents sprinklers user for fire-suppression. • It uses GENTRA to model the droplet paths. • Evaporation is considered, and is linked to the FLAIR humidity model. • The GENTRA inlet table is written automatically.

41. FLAIR Features • In addition, the following object types have been added: • Diffuser • Fire • Person • Crowd • Sunlight • Spray head • Jet fan

42. Jet fan

43. FLAIR applications FLAIR applications include:- • Clean rooms • Operating theatres • Sports arenas • Car parks • Road and rail tunnels • Industrial environments • Residential developments • Fire safety scenarios • Pollution control

44. Environmental Simulation The questions to be addressed: • Geometry and its representation • Domain Size • Grid Size • What Turbulence models • Conservation equations • Boundary conditions • Numerical scheme • Convergence

45. Geometry creationDWG---AutoCad  STL Facetfix might be needed if there are defects in the STL file.

46. Repairing holes with Facetfix

47. Geometry creationfrom a PDF file The numbers represent the height of the building

48. Geometry creation from a PDF file • The solution was to save the image as a GIF file, then use it as a backdrop in AC3D • We could trace round each part, then extrude

49. Geometry creation from a PDF file The resulting geometry was then exported to PHOENICS

50. Domain Size Generally, the boundary distance from the built area should be large enough in order that the physical boundary conditions can be reasonably specified as follows: • The upper boundary should provide zero axial pressure gradient; • The upstream boundary should be sufficiently far from the built area to ensure that the latter’s influence on the pressure field is negligible. • Location of the downstream and lateral boundaries should be well beyond any separation regions in the wake.