Download presentation

Presentation is loading. Please wait.

Published byClayton Burkart Modified about 1 year ago

1
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 When the convergence gets rough… MIGAL for PHOENICS

2
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Migal How to What’s happening Conclusion MFRDC is specialized in numerical methods and embedded scientific software MIGAL is a coupled multigrid solver that…

3
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Turns hours 8 hours 12 minutes into minutes Migal How to What’s happening Conclusion

4
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 And the more cells… the better… Migal How to What’s happening Conclusion

5
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 the better… Because segregated algorithms are at least N² because MIGAL is a fully coupled multi-grid solver almost N Migal How to What’s happening Conclusion

6
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Why? Migal How to What’s happening Conclusion

7
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 The Equations for U,V,W,P Migal How to What’s happening Conclusion

8
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Segregated Approach 1.Linearize, discretize and solve x- momentum equation for U 2.Linearize, discretize and solve y- momentum equation for V 3.Linearize, discretize and solve z- momentum equation for W 4.Linearize, discretize and solve mass equation for P 5.Back to step 1 until convergence Migal How to What’s happening Conclusion

9
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Segregated Approach LinearizeDiscretizeSolve Migal How to What’s happening Conclusion

10
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Segregated Approach LinearizeDiscretize Solve Migal How to What’s happening Conclusion

11
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Coupled Approach 1.Linearize and discretize momentum and mass equations in the same way than segragted approach 2.Solve by coupled solver for U,V,W,P 3.Back to step 1 until convergence Migal How to What’s happening Conclusion

12
Migal How to What’s happening Convergence Parameters Conclusion Coupled Approach Dr Michel Ferry September 2002 Migal How to What’s happening Conclusion

13
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Advantages 1.Segregated approach needs small time steps, especially when cell sizes diminish 2.Improving segregated solvers does not improve the over all convergence 3.Almost no time step restiriction for linear flows with the coupled approach 4.Improving the coupled solver (multi- grid) directly improves the over all convergence. Migal How to What’s happening Conclusion

14
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 How to… How to What’s happening Conclusion

15
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 How to control MIGAL? 2- by changing parameters 3- by extending to single variables 1- by Editing the q1 file 4- that’s all… How to What’s happening Conclusion

16
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 How to… How to What’s happening Conclusion

17
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 How to check MIGAL? 1- by openning the RESULT file 2- by looking for the MIGAL header 3- by looking for the sweeps outputs 4- that’s all… How to What’s happening Conclusion

18
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 How to check MIGAL? How to What’s happening Conclusion

19
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 What’s happening? How to What’s happening Conclusion

20
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Flow Past a Flat Plate UINI = WINI = 0 Z X How to What’s happening Conclusion

21
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 SIMPLEST’s first sweep How to What’s happening Conclusion

22
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 MIGAL’s first sweep How to What’s happening Conclusion

23
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 More sweeps with SIMPLEST? How to What’s happening Conclusion

24
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 More sweeps with SIMPLEST What for How to What’s happen New features More examples Conclusion isweep=1isweep=2isweep=3isweep=4isweep=15isweep=30isweep=45isweep=60isweep=300isweep=450isweep=1000isweep=1500

25
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Phew… How to What’s happening Conclusion

26
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 More sweeps with MIGAL? How to What’s happening Conclusion

27
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 More sweeps with MIGAL isweep=1isweep=2isweep=3isweep=4isweep=5isweep=10 How to What’s happening Conclusion

28
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Converged How to What’s happening Conclusion

29
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Flow Past a Flat Plate UINI = 0 WINI = 1 Z X How to What’s happening Conclusion

30
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 SIMPLEST’s first sweep How to What’s happening Conclusion

31
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 MIGAL’s first sweep How to What’s happening Conclusion

32
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 More sweeps with SIMPLEST? How to What’s happening Conclusion

33
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 More sweeps with SIMPLEST isweep=1isweep=2isweep=3isweep=4isweep=15 How to What’s happening Conclusion

34
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 More sweeps with SIMPLEST … How to What’s happening Conclusion

35
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 More sweeps with SIMPLEST isweep=1500 How to What’s happening Conclusion

36
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 More sweeps with MIGAL? How to What’s happening Conclusion

37
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 More sweeps with MIGAL isweep=1isweep=2isweep=3isweep=4isweep=10 How to What’s happening Conclusion

38
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Converged How to What’s happening Conclusion

39
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Free Convection in Cavity Laminar Ra=1.E5 How to What’s happening Conclusion

40
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 SIMPLEST convergence? How to What’s happening Conclusion

41
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 SIMPLEST (velocity) isweep=1isweep=2isweep=3isweep=4isweep=50isweep=100isweep=200isweep=500 How to What’s happening Conclusion

42
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 SIMPLEST (temperature) isweep=1isweep=2isweep=3isweep=4isweep=50isweep=100isweep=200isweep=500 How to What’s happening Conclusion

43
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 MIGAL convergence? How to What’s happening Conclusion

44
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 MIGAL (velocity) isweep=1isweep=2isweep=3isweep=4isweep=10isweep=20 How to What’s happening Conclusion

45
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 MIGAL (temperature) isweep=1isweep=2isweep=3isweep=4isweep=10isweep=20 How to What’s happening Conclusion

46
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 When the convergence gets rough Convergence

47
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Correct setting RELAX(V1,FALSDT, E+10) RELAX(W1,FALSDT, E+10) RELAX(TEMP,FALSDT, E+00) SPEDAT(SET,MIGAL,SOLVED1,C,HYDRO) SPEDAT(SET,MIGAL,LINRLX1,R,1.0000E+00) SPEDAT(SET,MIGAL,SOLVED2,C,TEMP) SPEDAT(SET,MIGAL,LINRLX2,R,1.0000E+00) RELAX(V1,FALSDT, E-02) RELAX(W1,FALSDT, E-02) RELAX(TEMP,FALSDT, E+00) SPEDAT(SET,MIGAL,SOLVED1,C,HYDRO) SPEDAT(SET,MIGAL,LINRLX1,R,1.0000E+00) SPEDAT(SET,MIGAL,SOLVED2,C,TEMP) SPEDAT(SET,MIGAL,LINRLX2,R,1.0000E+00) Ambitious setting Convergence

48
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 MIGAL (velocity) isweep=1isweep=2isweep=3isweep=4isweep=5isweep=6isweep=7 Convergence

49
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 MIGAL (temperature) isweep=1isweep=2isweep=3isweep=4isweep=5isweep=6isweep=7 Convergence

50
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Why? ok Convergence

51
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 RELAX(V1,FALSDT, E+10) RELAX(W1,FALSDT, E+10) RELAX(TEMP,FALSDT, E+00) SPEDAT(SET,MIGAL,SOLVED1,C,HYDRO) SPEDAT(SET,MIGAL,LINRLX1,R,5.0000E-01) SPEDAT(SET,MIGAL,SOLVED2,C,TEMP) SPEDAT(SET,MIGAL,LINRLX2,R,1.0000E+00) Alternative setting Convergence

52
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Non-linearities Convergence Convection -Momentum convection => quadradtic terms in momentum equations

53
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Non-linearities Convergence Buoyancy –Heat convection => density dependence to velocity field

54
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Non-linearities Convergence Turbulence –Convection of turbulent quantities (k, ) –Production term highly dependent on velocity gradients

55
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Non-linearities Convergence Non-Orthogonality –Missing terms in correction operator P E N S SE NE e x y P E N S SE NE e x y

56
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Non-linearities Convergence High-order schemes –Missing terms in correction operator P E W WW w

57
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Parameters When facing non-linear oscillations –Reduce time step –RELAX(U1,FALSDT,...) –RELAX(V1,FALSDT,...) –RELAX(W1,FALSDT,...) –Under-relax corrections –SPEDAT(MIGAL,LINRLX1,R,...) Parameters

58
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Parameters When facing poor linear convergence –Increase effort on each grid (very large grids) –SPEDAT(MIGAL,NBRELAX1,I,...) –SPEDAT(MIGAL,NBPRER1,I,...) –SPEDAT(MIGAL,LITER1,I,...) –SPEDAT(MIGAL,RESFAC1,R,...) Parameters cycle max mean rms E E E E E E E E E E E E E E E E E E-03 Restriction Prolongation Pre-Restriction relaxations Post-Prolongation relaxations Last level relaxations

59
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Parameters When facing strong local convergence issue –Use the multi-grid preconditionned GMRES facility –SPEDAT(MIGAL,IGMRES1,I,...) –SPEDAT(MIGAL,NBPRECO1,I,...) NB: Increase memory footprint! Parameters

60
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Parameters : GMRES cycle max mean rms E E E E E E E E E E E E E E E E E E-03 IGMRES = 0 cycle max mean rms E E E E E E E E E-04 IGMRES = 5 1 order 2 orders Parameters

61
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 More Examples? Parameters

62
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Turbulent (k- ) open cavity RELAX(V1,FALSDT, E-02) RELAX(W1,FALSDT, E-02) RELAX(KE,FALSDT, E-02) RELAX(EP,FALSDT, E-02) SPEDAT(SET,MIGAL,SOLVED1,C,HYDRO) SPEDAT(SET,MIGAL,LINRLX1,R,8.0000E-01) SPEDAT(SET,MIGAL,SOLVED2,C,KEMODL) SPEDAT(SET,MIGAL,LINRLX2,R,1.0000E+00) Parameters

63
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Comfort in a supermarket VARMAX(TEM1 ) = VARMIN(TEM1 ) = RELAX(U1,FALSDT, E+3) RELAX(V1,FALSDT, E+3) RELAX(W1,FALSDT, E+3) SPEDAT(MIGAL,SOLVED1,C,HYDRO) SPEDAT(MIGAL,LINRLX1,R,0.4) SPEDAT(MIGAL,IGMRES1,I,5) SPEDAT(MIGAL,RESFAC1,R,0.O) SPEDAT(MIGAL,SOLVED2,C,TEM1) SPEDAT(MIGAL,RESFAC2,R,0.0) SPEDAT(MIGAL,SOLVED3,C,KEMODL) SPEDAT(MIGAL,LINRLX3,R,0.8) SPEDAT(MIGAL,RESFAC3,R,0.0) Parameters

64
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Racing Car Model RELAX(U1,FALSDT, E+10) RELAX(V1,FALSDT, E+10) RELAX(W1,FALSDT, E+10) SPEDAT(MIGAL,SOLVED1,C,HYDRO) SPEDAT(MIGAL,LINRLX1,R,0.6) SPEDAT(MIGAL,IGMRES1,I,5) SPEDAT(MIGAL,RELAX1,R,0.85) SPEDAT(MIGAL,SOLVED2,C,KEMODL) SPEDAT(MIGAL,LINRLX2,R,0.8) SPEDAT(MIGAL,NBRELAX2,I,10) Parameters

65
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Conclusion

66
Migal How to What’s happening Convergence Parameters Conclusion Michel Ferry June 2008 Conclusion MIGAL boosts your convergence. MIGAL proceeds only few sweeps. Parameters can overcome usual convergence issues. Conclusion

Similar presentations

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google