|
[Sponsors] |
November 7, 2006, 13:46 |
For my approx 1.2 million cell
|
#1 |
Senior Member
Srinath Madhavan (a.k.a pUl|)
Join Date: Mar 2009
Location: Edmonton, AB, Canada
Posts: 703
Rep Power: 21 |
For my approx 1.2 million cells (single-phase) icoFoam vortex shedding case, here is the output after the first three time steps and the corresponding fvSolution pressure solver entries:
ICCG: (p ICCG 1e-06 0;) /*---------------------------------------------------------------------------*\ | ========= | | | \ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \ / O peration | Version: 1.3 | | \ / A nd | Web: http://www.openfoam.org | | \/ M anipulation | | \*---------------------------------------------------------------------------*/ Exec : /home/madhavan/OpenFOAM/OpenFOAM-1.3/applications/bin/linuxAMD64Gcc4DPOpt/icoFoa m /home/madhavan/OpenFOAM/madhavan-1.3/run/tutorials/icoFoam/. one_sq_cyl_3d_unsteady Date : Nov 07 2006 Time : 12:27:17 Host : masternode PID : 21882 Root : /home/madhavan/OpenFOAM/madhavan-1.3/run/tutorials/icoFoam/. Case : one_sq_cyl_3d_unsteady Nprocs : 1 Create time Create mesh for time = 0 Reading transportProperties Reading field p Reading field U Reading/calculating face flux field phi Reading probeLocations Constructing probes Starting time loop Time = 0.1 Mean and max Courant Numbers = 0 0.0741732 BICCG: Solving for Ux, Initial residual = 1, Final residual = 7.60531e-08, No Iterations 3 BICCG: Solving for Uy, Initial residual = 0, Final residual = 0, No Iterations 0 BICCG: Solving for Uz, Initial residual = 0, Final residual = 0, No Iterations 0 ICCG: Solving for p, Initial residual = 1, Final residual = 9.73006e-07, No Iterations 825 time step continuity errors : sum local = 4.55914e-10, global = -5.75299e-13, cumulative = -5.75299e-13 ICCG: Solving for p, Initial residual = 0.00108292, Final residual = 9.32198e-07, No Iterations 685 time step continuity errors : sum local = 3.75695e-07, global = -7.83026e-10, cumulative = -7.83601e-10 Wall patch = 0 Wall patch name = ChannelWalls Uav = (1 0 0) Aref = 1 nu = nu [0 2 -1 0 0 0 0] 1.004e-06 DragCoefficient = 2.01178e-05 pressureDragCoefficient = 0 viscDragCoefficient = 2.01178e-05 LiftCoefficient = 1.41566e-11 Wall patch = 1 Wall patch name = ObstacleWalls Uav = (1 0 0) Aref = 1 nu = nu [0 2 -1 0 0 0 0] 1.004e-06 DragCoefficient = 4.79068e-06 pressureDragCoefficient = 4.62468e-06 viscDragCoefficient = 1.66004e-07 LiftCoefficient = 8.15603e-14 ExecutionTime = 347.02 s ClockTime = 347 s Time = 0.2 Mean and max Courant Numbers = 0.108516 4.04533 BICCG: Solving for Ux, Initial residual = 0.823434, Final residual = 4.45773e-06, No Iterations 3 BICCG: Solving for Uy, Initial residual = 0.329552, Final residual = 3.46137e-06, No Iterations 4 BICCG: Solving for Uz, Initial residual = 0.362595, Final residual = 4.31759e-06, No Iterations 3 ICCG: Solving for p, Initial residual = 0.00371997, Final residual = 9.84174e-07, No Iterations 719 time step continuity errors : sum local = 1.53182e-07, global = 3.88971e-10, cumulative = -3.9463e-10 ICCG: Solving for p, Initial residual = 0.00419475, Final residual = 9.92882e-07, No Iterations 709 time step continuity errors : sum local = 7.36119e-08, global = -2.94289e-10, cumulative = -6.88919e-10 Wall patch = 0 Wall patch name = ChannelWalls Uav = (1 0 0) Aref = 1 nu = nu [0 2 -1 0 0 0 0] 1.004e-06 DragCoefficient = 2.11014e-05 pressureDragCoefficient = 0 viscDragCoefficient = 2.11014e-05 LiftCoefficient = 2.18023e-11 Wall patch = 1 Wall patch name = ObstacleWalls Uav = (1 0 0) Aref = 1 nu = nu [0 2 -1 0 0 0 0] 1.004e-06 DragCoefficient = -9.70849e-07 pressureDragCoefficient = -1.11824e-06 viscDragCoefficient = 1.47396e-07 LiftCoefficient = -2.70848e-11 ExecutionTime = 639.75 s ClockTime = 640 s ----------------------------------------------- ----------------------------------------------- AMG (p AMG 1e-06 0 1000;): /*---------------------------------------------------------------------------*\ | ========= | | | \ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \ / O peration | Version: 1.3 | | \ / A nd | Web: http://www.openfoam.org | | \/ M anipulation | | \*---------------------------------------------------------------------------*/ Exec : /home/madhavan/OpenFOAM/OpenFOAM-1.3/applications/bin/linuxAMD64Gcc4DPOpt/icoFoa m /home/madhavan/OpenFOAM/madhavan-1.3/run/tutorials/icoFoam/. one_sq_cyl_3d_unsteady Date : Nov 07 2006 Time : 11:29:35 Host : masternode PID : 21242 Root : /home/madhavan/OpenFOAM/madhavan-1.3/run/tutorials/icoFoam/. Case : one_sq_cyl_3d_unsteady Nprocs : 1 Create time Create mesh for time = 0 Reading transportProperties Reading field p Reading field U Reading/calculating face flux field phi Reading probeLocations Constructing probes Starting time loop Time = 0.1 Mean and max Courant Numbers = 0 0.0741732 BICCG: Solving for Ux, Initial residual = 1, Final residual = 7.60531e-08, No Iterations 3 BICCG: Solving for Uy, Initial residual = 0, Final residual = 0, No Iterations 0 BICCG: Solving for Uz, Initial residual = 0, Final residual = 0, No Iterations 0 AMG: Solving for p, Initial residual = 1, Final residual = 9.80164e-07, No Iterations 105 time step continuity errors : sum local = 4.59248e-10, global = 2.47297e-14, cumulative = 2.47297e-14 AMG: Solving for p, Initial residual = 0.00108292, Final residual = 9.69421e-07, No Iterations 48 time step continuity errors : sum local = 3.90696e-07, global = -1.15826e-11, cumulative = -1.15579e-11 Wall patch = 0 Wall patch name = ChannelWalls Uav = (1 0 0) Aref = 1 nu = nu [0 2 -1 0 0 0 0] 1.004e-06 DragCoefficient = 2.01179e-05 pressureDragCoefficient = 0 viscDragCoefficient = 2.01179e-05 LiftCoefficient = -5.64623e-09 Wall patch = 1 Wall patch name = ObstacleWalls Uav = (1 0 0) Aref = 1 nu = nu [0 2 -1 0 0 0 0] 1.004e-06 DragCoefficient = 4.79158e-06 pressureDragCoefficient = 4.62556e-06 viscDragCoefficient = 1.6602e-07 LiftCoefficient = 1.45852e-10 ExecutionTime = 146.7 s ClockTime = 147 s Time = 0.2 Mean and max Courant Numbers = 0.108519 4.04592 BICCG: Solving for Ux, Initial residual = 0.823441, Final residual = 4.46106e-06, No Iterations 3 BICCG: Solving for Uy, Initial residual = 0.329408, Final residual = 3.4621e-06, No Iterations 4 BICCG: Solving for Uz, Initial residual = 0.362669, Final residual = 4.339e-06, No Iterations 3 AMG: Solving for p, Initial residual = 0.0037213, Final residual = 9.14087e-07, No Iterations 82 time step continuity errors : sum local = 1.42274e-07, global = -4.78435e-13, cumulative = -1.20363e-11 AMG: Solving for p, Initial residual = 0.00419589, Final residual = 9.94429e-07, No Iterations 75 time step continuity errors : sum local = 7.37282e-08, global = 1.93804e-13, cumulative = -1.18425e-11 Wall patch = 0 Wall patch name = ChannelWalls Uav = (1 0 0) Aref = 1 nu = nu [0 2 -1 0 0 0 0] 1.004e-06 DragCoefficient = 2.11013e-05 pressureDragCoefficient = 0 viscDragCoefficient = 2.11013e-05 LiftCoefficient = 8.69834e-09 Wall patch = 1 Wall patch name = ObstacleWalls Uav = (1 0 0) Aref = 1 nu = nu [0 2 -1 0 0 0 0] 1.004e-06 DragCoefficient = -9.72347e-07 pressureDragCoefficient = -1.11973e-06 viscDragCoefficient = 1.47384e-07 LiftCoefficient = -2.83295e-10 ExecutionTime = 294.14 s ClockTime = 295 s ------------------------------------------- ------------------------------------------- AMG (p AMG 1e-06 0 100;): /*---------------------------------------------------------------------------*\ | ========= | | | \ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \ / O peration | Version: 1.3 | | \ / A nd | Web: http://www.openfoam.org | | \/ M anipulation | | \*---------------------------------------------------------------------------*/ Exec : /home/madhavan/OpenFOAM/OpenFOAM-1.3/applications/bin/linuxAMD64Gcc4DPOpt/icoFoa m /home/madhavan/OpenFOAM/madhavan-1.3/run/tutorials/icoFoam/. one_sq_cyl_3d_unsteady Date : Nov 07 2006 Time : 12:20:05 Host : masternode PID : 21848 Root : /home/madhavan/OpenFOAM/madhavan-1.3/run/tutorials/icoFoam/. Case : one_sq_cyl_3d_unsteady Nprocs : 1 Create time Create mesh for time = 0 Reading transportProperties Reading field p Reading field U Reading/calculating face flux field phi Reading probeLocations Constructing probes Starting time loop Time = 0.1 Mean and max Courant Numbers = 0 0.0741732 BICCG: Solving for Ux, Initial residual = 1, Final residual = 7.60531e-08, No Iterations 3 BICCG: Solving for Uy, Initial residual = 0, Final residual = 0, No Iterations 0 BICCG: Solving for Uz, Initial residual = 0, Final residual = 0, No Iterations 0 AMG: Solving for p, Initial residual = 1, Final residual = 8.07098e-07, No Iterations 102 time step continuity errors : sum local = 3.78169e-10, global = 1.46199e-14, cumulative = 1.46199e-14 AMG: Solving for p, Initial residual = 0.00108292, Final residual = 8.70596e-07, No Iterations 48 time step continuity errors : sum local = 3.50868e-07, global = 3.39341e-10, cumulative = 3.39356e-10 Wall patch = 0 Wall patch name = ChannelWalls Uav = (1 0 0) Aref = 1 nu = nu [0 2 -1 0 0 0 0] 1.004e-06 DragCoefficient = 2.01179e-05 pressureDragCoefficient = 0 viscDragCoefficient = 2.01179e-05 LiftCoefficient = -4.35326e-09 Wall patch = 1 Wall patch name = ObstacleWalls Uav = (1 0 0) Aref = 1 nu = nu [0 2 -1 0 0 0 0] 1.004e-06 DragCoefficient = 4.79156e-06 pressureDragCoefficient = 4.62554e-06 viscDragCoefficient = 1.6602e-07 LiftCoefficient = 8.678e-11 ExecutionTime = 108.75 s ClockTime = 109 s Time = 0.2 Mean and max Courant Numbers = 0.10852 4.04587 BICCG: Solving for Ux, Initial residual = 0.823445, Final residual = 4.46093e-06, No Iterations 3 BICCG: Solving for Uy, Initial residual = 0.329439, Final residual = 3.4626e-06, No Iterations 4 BICCG: Solving for Uz, Initial residual = 0.362502, Final residual = 4.33196e-06, No Iterations 3 AMG: Solving for p, Initial residual = 0.00372114, Final residual = 7.40435e-07, No Iterations 68 time step continuity errors : sum local = 1.15246e-07, global = -2.12212e-12, cumulative = 3.37234e-10 AMG: Solving for p, Initial residual = 0.00419577, Final residual = 9.12739e-07, No Iterations 60 time step continuity errors : sum local = 6.76724e-08, global = 1.6342e-11, cumulative = 3.53576e-10 Wall patch = 0 Wall patch name = ChannelWalls Uav = (1 0 0) Aref = 1 nu = nu [0 2 -1 0 0 0 0] 1.004e-06 DragCoefficient = 2.11013e-05 pressureDragCoefficient = 0 viscDragCoefficient = 2.11013e-05 LiftCoefficient = 7.399e-09 Wall patch = 1 Wall patch name = ObstacleWalls Uav = (1 0 0) Aref = 1 nu = nu [0 2 -1 0 0 0 0] 1.004e-06 DragCoefficient = -9.72242e-07 pressureDragCoefficient = -1.11963e-06 viscDragCoefficient = 1.47384e-07 LiftCoefficient = -2.05608e-10 ExecutionTime = 191.77 s ClockTime = 192 s Clearly, the AMG solver is better than ICCG for this case. Are there any guidelines on what number to use at the coarsest level for the AMG solver? |
|
November 7, 2006, 14:49 |
On the top level of AMG you ha
|
#2 |
Senior Member
Hrvoje Jasak
Join Date: Mar 2009
Location: London, England
Posts: 1,906
Rep Power: 33 |
On the top level of AMG you have a system of equations that needs to be solved to a tight tolerance and the question is how much work to leave for the top level. In serial runs, anything between a dozen and a couple of hundred cells will give you the same result (1000 is too much). In parallel, it is the communications that matter, which means you need to be more careful: make sure there's a sufficient number of cells for each CPU. You also need to worry about the case where you have multiple separate domains. In general, 20-30 cells per CPU in parallel will do you fine (until I do some more tricks to speed this up). :-)
Hrv
__________________
Hrvoje Jasak Providing commercial FOAM/OpenFOAM and CFD Consulting: http://wikki.co.uk |
|
November 7, 2006, 15:15 |
Thanks for that insightful rep
|
#3 |
Senior Member
Srinath Madhavan (a.k.a pUl|)
Join Date: Mar 2009
Location: Edmonton, AB, Canada
Posts: 703
Rep Power: 21 |
Thanks for that insightful reply Hrv. Much appreciated.
|
|
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Dissimilarity in compiling new BC in 32bit OpenSuSE 103 versus 64bit CentOS 50 versus 64bit SLED 100 | sponiar | OpenFOAM Running, Solving & CFD | 3 | February 26, 2008 06:31 |
RIPPLE ICCG diverge | brian | CFX | 0 | February 24, 2007 00:26 |
AMG vs ICCG | eugene | OpenFOAM Running, Solving & CFD | 2 | June 7, 2005 14:07 |
[ICCG, CGSTAB ?] | name | Main CFD Forum | 1 | September 13, 2001 11:13 |
ICCG / ILU routines | Jin Li | Main CFD Forum | 0 | June 24, 2000 05:45 |