[Jinjolee]

Recently, I tried to run my simulation using simpleFoam, but then I found the residual and forceCoeffs fluctuate a lot, so I think it may have a transient solution, and then switched to pisoFoam.
I kept most of the file unchanged, except:
controlDict(change from "simpleFoam" to "pisoFoam"),
fvSchemes(modified using $FOAM_TUTORIALS/incompressible/pisoFoam/RAS/cavity as reference),
fvSolution(same as above)

Then I tried to run it again, but the pisoFoam went wrong. It aborted, but I have no idea what is the cause. The log.pisoFoam:

--------------------------------------------------------------------------
WARNING: Linux kernel CMA support was requested via the
btl_vader_single_copy_mechanism MCA variable, but CMA support is
not available due to restrictive ptrace settings.

The vader shared memory BTL will fall back on another single-copy
mechanism if one is available. This may result in lower performance.

  Local host: AdminPC
--------------------------------------------------------------------------
/*---------------------------------------------------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     | Website:  https://openfoam.org
    \\  /    A nd           | Version:  dev
     \\/     M anipulation  |
\*---------------------------------------------------------------------------*/
Build  : dev-becf7d290547
Exec   : pisoFoam -parallel
Date   : Apr 27 2019
Time   : 02:15:36
Host   : "AdminPC"
PID    : 656
I/O    : uncollated
Case   : /home/taeioum/OpenFOAM/taeioum-dev/run/constantMovingTest/c3t
nProcs : 6
Slaves : 
5
(
"AdminPC.657"
"AdminPC.658"
"AdminPC.659"
"AdminPC.660"
"AdminPC.661"
)

Pstream initialized with:
    floatTransfer      : 0
    nProcsSimpleSum    : 0
    commsType          : nonBlocking
    polling iterations : 0
sigFpe : Enabling floating point exception trapping (FOAM_SIGFPE).
fileModificationChecking : Monitoring run-time modified files using timeStampMaster (fileModificationSkew 10)
allowSystemOperations : Allowing user-supplied system call operations

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create time

Create mesh for time = 0

Reading field p

Reading field U

Reading/calculating face flux field phi

Selecting incompressible transport model Newtonian
Selecting turbulence model type RAS
Selecting RAS turbulence model kEpsilon
RAS
{
    RASModel        kEpsilon;
    turbulence      on;
    printCoeffs     on;
    Cmu             0.09;
    C1              1.44;
    C2              1.92;
    C3              0;
    sigmak          1;
    sigmaEps        1.3;
}

No MRF models present

No finite volume options present

Starting time loop

streamLine streamLines:
    automatic track length specified through number of sub cycles : 5

[AdminPC:00651] 5 more processes have sent help message help-btl-vader.txt / cma-permission-denied
[AdminPC:00651] Set MCA parameter "orte_base_help_aggregate" to 0 to see all help / error messages
Reading surface description:
    yNormal

forces forceCoeffs1:
    Not including porosity effects
forceCoeffs forceCoeffs1:
    Not including porosity effects
Time = 0.05

Courant Number mean: 0.0135004 max: 0.861136
smoothSolver:  Solving for Ux, Initial residual = 1, Final residual = 7.22412e-06, No Iterations 4
smoothSolver:  Solving for Uy, Initial residual = 1, Final residual = 9.52946e-06, No Iterations 4
smoothSolver:  Solving for Uz, Initial residual = 1, Final residual = 5.33646e-06, No Iterations 5
-------------------------------------------------------
Primary job  terminated normally, but 1 process returned
a non-zero exit code.. Per user-direction, the job has been aborted.
-------------------------------------------------------
--------------------------------------------------------------------------
mpirun detected that one or more processes exited with non-zero status, thus causing
the job to be terminated. The first process to do so was:

  Process name: [[9700,1],3]
  Exit code:    145
--------------------------------------------------------------------------

Does anyone know what happen? Thanks

[Jinjolee]

The problem seems to be solved by reducing the timestep.
Originally I got a deltaTime of 0.05s, and now I got 0.005s.
The calculation is now able to proceed.
Is there any timestep limitation on pisoFoam? Or did I just solve this problem with luck?

[RobertHB]

Originally Posted by Jinjolee

Is there any timestep limitation on pisoFoam?

Yes, it's called the Courant number. The values has to stay below 1.0.

[Jinjolee]

Originally Posted by RobertHB

Yes, it's called the Courant number. The values has to stay below 1.0.

Thanks a lot. I have never done transient solution before. Now I got it.