CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Running, Solving & CFD

Divergence in parallel running after case reconstruction

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   September 26, 2022, 04:42
Default Divergence in parallel running after case reconstruction
  #1
New Member
 
Hung
Join Date: Dec 2021
Posts: 1
Rep Power: 0
nguyenhung97 is on a distinguished road
Hi all!

I am running a simulation in a very complex geometry (human lung). Due to computer resources, I sometimes have to share clusters to other shared users. I constantly have to change my running processor number to 36, 72, 108, ... That's why I reconstruct and decompose the case again if I want to use different number of processor. My process is:

1. When someone asks for nodes, I stop my case (running in 108 cores) and reconstructPar -latestTime.
2. Then I decomposePar -latestTime the case to 36 cores and restart. This is when I face a divergence problem.

You can refer to the following results. After the second decomposing, my max parallel Courant number is 10.791 at time 0.1424 and keep doubling until divergence.

Quote:
Time = 0.1421s

Courant Number mean: 0.050839 max: 10.791
smoothSolver: Solving for Ux, Initial residual = 0.0138731, Final residual = 1.87886e-05, No Iterations 2
smoothSolver: Solving for Uy, Initial residual = 0.00704013, Final residual = 8.98269e-06, No Iterations 2
smoothSolver: Solving for Uz, Initial residual = 0.00496356, Final residual = 5.72542e-05, No Iterations 1
GAMG: Solving for p, Initial residual = 0.446619, Final residual = 5.04061e-05, No Iterations 13
GAMG: Solving for p, Initial residual = 0.182663, Final residual = 7.16055e-05, No Iterations 9
time step continuity errors : sum local = 6.20123e-08, global = -9.05988e-11, cumulative = -1.4971e-08
Current Inlet Flow Rate = -1.92092e-05
Current Inlet Flow Rate = -1.92092e-05
GAMG: Solving for p, Initial residual = 0.077038, Final residual = 8.26782e-05, No Iterations 8
GAMG: Solving for p, Initial residual = 0.0238152, Final residual = 8.96751e-05, No Iterations 4
time step continuity errors : sum local = 7.20512e-08, global = -1.06162e-09, cumulative = -1.60326e-08
Current Inlet Flow Rate = -1.92092e-05
GAMG: Solving for p, Initial residual = 0.0158456, Final residual = 8.69424e-05, No Iterations 6
GAMG: Solving for p, Initial residual = 0.00734297, Final residual = 8.69807e-05, No Iterations 3
time step continuity errors : sum local = 7.1083e-08, global = -3.9716e-10, cumulative = -1.64297e-08
Current Inlet Flow Rate = -1.92092e-05
GAMG: Solving for p, Initial residual = 0.00314104, Final residual = 5.60797e-05, No Iterations 3
GAMG: Solving for p, Initial residual = 0.00113054, Final residual = 7.12193e-07, No Iterations 7
time step continuity errors : sum local = 5.8211e-10, global = 4.59426e-11, cumulative = -1.63838e-08
Current Inlet Flow Rate = -1.92092e-05
ExecutionTime = 332.33 s ClockTime = 333 s
But when I try to run in one processor, it is only 5.50062 and keep running stably.

Quote:
Time = 0.1424s

Courant Number mean: 0.0509005 max: 5.50062
smoothSolver: Solving for Ux, Initial residual = 0.000300878, Final residual = 5.47137e-07, No Iterations 1
smoothSolver: Solving for Uy, Initial residual = 0.000388301, Final residual = 6.99841e-07, No Iterations 1
smoothSolver: Solving for Uz, Initial residual = 0.000328347, Final residual = 5.75167e-07, No Iterations 1
GAMG: Solving for p, Initial residual = 0.00066149, Final residual = 7.38323e-05, No Iterations 1
GAMG: Solving for p, Initial residual = 0.000248216, Final residual = 2.83435e-05, No Iterations 1
time step continuity errors : sum local = 1.15499e-08, global = 1.48838e-11, cumulative = -1.21772e-09
Current Inlet Flow Rate = -1.92498e-05
Current Inlet Flow Rate = -1.92498e-05
GAMG: Solving for p, Initial residual = 0.000128847, Final residual = 1.38249e-05, No Iterations 1
GAMG: Solving for p, Initial residual = 4.03098e-05, Final residual = 4.03098e-05, No Iterations 0
time step continuity errors : sum local = 1.64264e-08, global = -4.7946e-11, cumulative = -1.26567e-09
Current Inlet Flow Rate = -1.92498e-05
GAMG: Solving for p, Initial residual = 4.08922e-05, Final residual = 4.08922e-05, No Iterations 0
GAMG: Solving for p, Initial residual = 4.08922e-05, Final residual = 4.08922e-05, No Iterations 0
time step continuity errors : sum local = 1.66638e-08, global = -4.7946e-11, cumulative = -1.31361e-09
Current Inlet Flow Rate = -1.92498e-05
GAMG: Solving for p, Initial residual = 4.09558e-05, Final residual = 4.09558e-05, No Iterations 0
GAMG: Solving for p, Initial residual = 4.09558e-05, Final residual = 9.72793e-07, No Iterations 2
time step continuity errors : sum local = 3.96418e-10, global = 6.94878e-12, cumulative = -1.30666e-09
Current Inlet Flow Rate = -1.92498e-05
Note: I tried to reduce the time step to 1e-5 1e-6 (originally 1e-4) and still didn't solve the problem.

Anyone has any idea? Thanks.
nguyenhung97 is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
[mesh manipulation] Case diverges after running renumberMesh in parallel sita OpenFOAM Meshing & Mesh Conversion 1 June 26, 2019 08:24
Running AMI case in parallel Kaskade OpenFOAM Running, Solving & CFD 3 March 14, 2016 16:58
Is Playstation 3 cluster suitable for CFD work hsieh OpenFOAM 9 August 16, 2015 15:53
Running in parallel Djub OpenFOAM Running, Solving & CFD 3 January 24, 2013 17:01
Free surface boudary conditions with SOLA-VOF Fan Main CFD Forum 10 September 9, 2006 13:24


All times are GMT -4. The time now is 15:54.