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MIGAL for Phoenics 3.3

MIGAL for Phoenics 3.3. The New Coupled Algebraic Multi-grid Solver. 8 HOURS !!!!. Which computer could run PHOENICS 5, 10 or 30 times faster ?. yours. Yours. Yours with MIGAL. 12 mn. Instead of SIMPLEST. The Problem. Simple, Simpler, Simplec, Simplest, Piso are segregating algorithms

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MIGAL for Phoenics 3.3

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  1. MIGAL for Phoenics 3.3 The New Coupled Algebraic Multi-grid Solver

  2. 8 HOURS !!!!

  3. Which computer could run PHOENICS5, 10 or 30 times faster ?

  4. yours Yours

  5. Yours with MIGAL 12 mn

  6. Instead of SIMPLEST

  7. The Problem • Simple, Simpler, Simplec, Simplest, Piso are segregating algorithms • Then they need under-relaxation to ensure stability of the velocity-pressure coupling (FALSDT) • They are at least N2 algorithm

  8. SIMPLEST CPU

  9. The Idea • A better perfomance of the solver for each equation separatly IS NOT the solution • We must solve implicitly the velocity-pressure coupling before accelerating with multi-grid

  10. How ? • Linearize the momentum equations but do not solve • Build the continuity equation • Solve the algebraic system composed of 3x3 or 4x4 blocs :SAnbfnb = S fnb= S = Anb=

  11. But... • The CPU time cost per sweep increase (x10) • Additional storage is needed (70 Mb for 100,000 3D cells) Mb/cell Staggered Co-locative 2D 4.E-4 3.E-4 3D 7.E-4 5.E-4

  12. 3D RAM

  13. 2D RAM

  14. RAM vs CPU : the Winning Bet

  15. Library Cases • 2D Lid-Driven Cavity Re=10,000

  16. Library Cases • 2D Lid-Driven Cavity Re=10,000 • 2D Flow Past a Flat Plate Re=10

  17. Library Cases • 2D Lid-Driven Cavity Re=10,000 • 2D Flow Past a Flat Plate Re=10 • 2D Flow in Unit of Staggered Tube Bank

  18. Library Cases • 2D Lid-Driven Cavity Re=10,000 • 2D Flow Past a Flat Plate Re=10 • 2D Flow in Unit of Staggered Tube Bank • 2D Laminar Backward Facing Step

  19. Library Cases • 2D Lid-Driven Cavity Re=10,000 • 2D Flow Past a Flat Plate Re=10 • 2D Flow in Unit of Staggered Tube Bank • 2D Laminar Backward Facing Step • 2D Turbulent Backward Facing Step

  20. Library Cases • 2D Lid-Driven Cavity Re=10,000 • 2D Flow Past a Flat Plate Re=10 • 2D Flow in Unit of Staggered Tube Bank • 2D Laminar Backward Facing Step • 2D Turbulent Backward Facing Step • 3D Flow Around a Group of Building

  21. Library Cases • 2D Lid-Driven Cavity Re=10,000 • 2D Flow Past a Flat Plate Re=10 • 2D Flow in Unit of Staggered Tube Bank • 2D Laminar Backward Facing Step • 2D Turbulent Backward Facing Step • 3D Flow Around a Group of Building • 3D Lid-Driven Cavity Re=1,000

  22. 2D Lid-Driven Cavity Re=10,000 872 - 1332 - 1662 - 1942 - 2182 - 2402 - 2602

  23. 2D Cavity CPU

  24. 2D Cavity Speed-up

  25. 2D Flow Past a Flat Plate Re=1020x70 - 40x140 - 52x190

  26. 2D Plate CPU

  27. 2D Plate Speed-up

  28. Flow in Symmetry Unit of Staggered Tub Bank Re=14010x21 - 50x105 - 100x210

  29. Tube bank CPU

  30. Tube Bank Speed-up

  31. Backward Facing Step Laminar Re=150

  32. Bstep_L CPU

  33. Bstep_L Speed_up

  34. Backward Facing Step Turbulent Quick-Koren (65x30) Re = 50,000

  35. Backward Facing Step (turbulent 65x30)

  36. 3D Flow Around Buildings

  37. Buildings CPU

  38. Buildings Speed-up

  39. 3D Lid-Driven Cavity Re=1,000 103 - 273 - 343 - 393 - 433 - 473

  40. 3D Cavity CPU

  41. 3D Cavity Speed-up

  42. How to use MIGAL for Phoenics ?

  43. Activating MIGAL (1/2) • Set large false time steps • relax(U1, falsdt, 1.E+10) • relax(V1, falsdt, 1.E+10) • relax(W1, falsdt, 1.E+10) • Activate MIGAL for pressure-velocity • spedat(MIGAL, SOLVED1, c, HYDRO)

  44. Activating MIGAL (2/2) • Activate MIGAL for scalar variables • spedat(MIGAL, SOLVED3, c, SMOKE) • Change default parameters • spedat(MIGAL, RELAX1, r, 0.9) • spedat(MIGAL, LITER3, i, 3)

  45. Conclusion • Coupled Multi-grid Method are already of great interest for 2D and 3D flows. • and will be unbeatable in the future. • MIGAL is boosting Phoenics with large speed-ups increasing with the number of cells.

  46. Roadmap for MIGAL With an affordable PC under 2500$

  47. WWW.mfrdc.com michel.ferry@mfrdc.com

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