SimScale CAE Forum

Error on CFD simulations

HI
my name is jurica and i am currently working on CFD simulations on formula student project.
the problem i have i keep geting errors at 37 min and i dont know why i check logs but i couldnt find out what is the problem. mesh have around 89 illegal cells but i dont think that is problem. so if anybody had same problem with it and solve it i would be very grateful on solution

link of project:
https://www.simscale.com/projects/rrtim/aero-/
https://www.simscale.com/workbench/?pid=2563677071864045635#tab_0-0

Hi @rrtim!

Having a look at this - will get back to you as soon as I know more.

Update: Make sure that you put in the right coordinates for PREDNJI & STRAZNJI, you can get the mid points for the wheels from a CAD software of your choice. X & Y-coordinate are the same only Z changes in this case.

Let me know if that helped!


Best,

Jousef

nope it didnt help.

maybe you can spot problem here?
/---------------------------------------------------------------------------
| ========= | |
| \ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \ / O peration | Version: 2.3.1 |
| \ / A nd | Web: www.OpenFOAM.org |
| \/ M anipulation | |
*---------------------------------------------------------------------------/
Build : 2.3.1-262087cdf8db
Exec : simpleFoam -parallel
Date : Oct 14 2018
Time : 07:44:37
Host : “”
PID : 150
Case :
nProcs : 16
Slaves :
15
(
“.151”
“.152”
“.153”
“.154”
“.155”
“.156”
“.157”
“.158”
“.159”
“.160”
“.161”
“.162”
“.163”
“.164”
“.165”
)
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
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 RAS turbulence model kOmegaSST
kOmegaSSTCoeffs
{
alphaK1 0.85;
alphaK2 1;
alphaOmega1 0.5;
alphaOmega2 0.856;
gamma1 0.555555555556;
gamma2 0.44;
beta1 0.075;
beta2 0.0828;
betaStar 0.09;
a1 0.31;
b1 1;
c1 10;
F3 false;
}
Creating finite volume options from “system/fvOptions”
SIMPLE: convergence criteria
field U tolerance 1e-05
field "p.
" tolerance 1e-05
field k tolerance 1e-05
field omega tolerance 1e-05
Starting time loop
–> FOAM Warning :
From function writeOldTimesOnSignalFunctionObject::writeOldTimesOnSignalFunctionObject
in file misc/writeOldTimesOnSignal/writeOldTimesOnSignal.C at line 84
‘writeCurrent’ was set. This may lead to uncaught segmentation faults
–> FOAM Warning :
From function writeOldTimesOnSignalFunctionObject::writeOldTimesOnSignalFunctionObject
in file misc/writeOldTimesOnSignal/writeOldTimesOnSignal.C at line 105
sigTERM unset. Setting it to true so that signal is propagated to other processors
If this is undesired explicitly set ‘sigTERM false;’ in “system/controlDict.functions.sigHandler”
[0] Set SIGFPE(8) signal handler
To switch this off set ‘sigFPE false;’
[0] Set SIGSEGV(11) signal handler
To switch this off set ‘sigSEGV false;’
To catch Ctrl-C set ‘sigINT true;’
[0] Set SIGTERM(15) signal handler
[0] Set SIGQUIT(3) signal handler
To catch the USR1-signal set ‘sigUSR1 true;’
To catch the USR2-signal set ‘sigUSR2 true;’
4 signal handlers installed
[1] Set SIGFPE(8) signal handler
[1] Set SIGSEGV(11) signal handler
[1] Set SIGTERM(15) signal handler
[1] Set SIGQUIT(3) signal handler
[2] Set SIGFPE(8) signal handler
[2] Set SIGSEGV(11) signal handler
[2] Set SIGTERM(15) signal handler
[2] Set SIGQUIT(3) signal handler
[3] Set SIGFPE(8) signal handler
[3] Set SIGSEGV(11) signal handler
[3] Set SIGTERM(15) signal handler
[3] Set SIGQUIT(3) signal handler
[5] Set SIGFPE(8) signal handler
[5] Set SIGSEGV(11) signal handler
[5] Set SIGTERM(15) signal handler
[5] Set SIGQUIT(3) signal handler
[6] Set SIGFPE(8) signal handler
[6] Set SIGSEGV(11) signal handler
[6] Set SIGTERM(15) signal handler
[6] Set SIGQUIT(3) signal handler
[9] Set SIGFPE(8) signal handler
[9] Set SIGSEGV(11) signal handler
[9] Set SIGTERM(15) signal handler
[9] Set SIGQUIT(3) signal handler
[12] Set SIGFPE(8) signal handler
[12] Set SIGSEGV(11) signal handler
[12] Set SIGTERM(15) signal handler
[12] Set SIGQUIT(3) signal handler
[13] Set SIGFPE(8) signal handler
[13] Set SIGSEGV(11) signal handler
[13] Set SIGTERM(15) signal handler
[13] Set SIGQUIT(3) signal handler
[14] Set SIGFPE(8) signal handler
[14] Set SIGSEGV(11) signal handler
[14] Set SIGTERM(15) signal handler
[14] Set SIGQUIT(3) signal handler
[15] Set SIGFPE(8) signal handler
[15] Set SIGSEGV(11) signal handler
[15] Set SIGTERM(15) signal handler
[15] Set SIGQUIT(3) signal handler
[4] Set SIGFPE(8) signal handler
[4] Set SIGSEGV(11) signal handler
[4] Set SIGTERM(15) signal handler
[4] Set SIGQUIT(3) signal handler
[7] Set SIGFPE(8) signal handler
[7] Set SIGSEGV(11) signal handler
[7] Set SIGTERM(15) signal handler
[7] Set SIGQUIT(3) signal handler
[8] Set SIGFPE(8) signal handler
[8] Set SIGSEGV(11) signal handler
[8] Set SIGTERM(15) signal handler
[8] Set SIGQUIT(3) signal handler
[10] Set SIGFPE(8) signal handler
[10] Set SIGSEGV(11) signal handler
[10] Set SIGTERM(15) signal handler
[10] Set SIGQUIT(3) signal handler
[11] Set SIGFPE(8) signal handler
[11] Set SIGSEGV(11) signal handler
[11] Set SIGTERM(15) signal handler
[11] Set SIGQUIT(3) signal handler
forces forces10:
Not including porosity effects
forces forces11:
Not including porosity effects
forces forces12:
Not including porosity effects
Time = 1
smoothSolver: Solving for Ux, Initial residual = 0.023856188765, Final residual = 0.000109506282281, No Iterations 6
smoothSolver: Solving for Uy, Initial residual = 0.0248066097167, Final residual = 0.000241574964413, No Iterations 5
smoothSolver: Solving for Uz, Initial residual = 0.0212609155836, Final residual = 0.000100702670271, No Iterations 6
GAMG: Solving for p, Initial residual = 1, Final residual = 0.00960066015176, No Iterations 8

Hi @rrtim!

Sure, will see what I can do here :slight_smile: Might take some time though just to let you know.

Cheers,

Jousef

hi @jousefm
i solve problem with error
i defined MRF zone on "rim"and it didnt caused any error in sim.
but now i am solving “problem” with convergence


should i try to better refine mesh or something else ?
i think results of undertray is seeming a little bit low

Hi @rrtim!

When having a look at the model it still seems that the point is not inside the middle but you said it was not the error - what was it then? Only numerical settings?

For the fineness of the mesh “simply” do a convergence study to see if values like forces saturate up to a certain point when decreasing the mesh size. @Get_Barried and @vgon_alves might add their two cents here as well.

Best,

Jousef

Hi @rrtim,

The divergence is probably caused by the illegal cells within your mesh. The geometry used in the simulation that diverged had around 67 illegal cells. While this is not a lot and I have seen simulations with geometries with over 200-300 illegal cells run well without any divergence, in your particular case you many not be as fortunate.

You’ve already adjusted the numerics to compensate for this and it is still not enough. I suggest trying to use a cellLimited Gauss linear scheme and a smooth solver for the pressure as well to try to see if the simulation can stop diverging without needing a re-mesh. If this does not work, then you will need to refine your mesh and lower not only the illegal cell count, but also increase the overall quality of the mesh as specific areas where the geometry is small.

Refer to the figures below to see where possible improvement and care must be taken with regards to increasing mesh quality.

Let us know how it goes.

Cheers.

Regards,
Barry

2 Likes

@Get_Barried
hi i tried setup you suggest and it didnt quite work


so i will try to improve mesh quality and see how that goes

Cheers

Hi @rrtim,

I just checked that simulation that you’ve posted. Did you cancel the run? There was no indication that the solver auto canceled.

The simulation was actually in the process of converging. Referring to the force plots below, you can see that the numerical solution is starting to reach some sort of oscillatory convergence and maybe a steady-state if you’re lucky. I suggest letting the sim run all the way till the end time of 1500s and see what the final solution is.

FW

Dif

body+head

Cheers.

Regards,
Barry

1 Like

@Get_Barried
hi
i tried with new mesh and i tried 2 types of setings
the first one is one which you recommended and convergence plot look like this


the second run i used settings as they were before and convergence plot look like this:

results are same. so i will try to set a longer time then 1500sec and i think it will be enough
i just wana thank to @jousefm and @Get_Barried you guys helped me a lot and for that i am really thankful

Cheers.

3 Likes