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How to solve problem diverging in OpenFOAM

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Old   April 5, 2018, 03:40
Default How to solve problem diverging in OpenFOAM
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Hi,

I got this error below when running a hypersonic flow problem. The problem has been adpted from the wedge15Ma5 example. May I know what it means?

I've tried many interpolation schemes but only upwind works. However, it is only 1st order. I hope to use other schemes which are 2nd order. What can I do to prevent divergence?

I have lowered deltaT, maxCo etc

[3] #0 Foam::error:rintStack(Foam::Ostream&) at ??:?
[3] #1 Foam::sigFpe::sigHandler(int) at ??:?
[3] #2 ? in "/lib64/libc.so.6"
[3] #3 Foam::hePsiThermo<Foam:siThermo, Foam:ureMixture<Foam::sutherlandTransport<Foam:: species::thermo<Foam::hConstThermo<Foam:erfectGa s<Foam::specie> >, Foam::sensibleInternalEnergy> > > >::calculate() at ??:?
[3] #4 Foam::hePsiThermo<Foam:siThermo, Foam:ureMixture<Foam::sutherlandTransport<Foam:: species::thermo<Foam::hConstThermo<Foam:erfectGa s<Foam::specie> >, Foam::sensibleInternalEnergy> > > >::correct() at ??:?
[3] #5 ? at ??:?
[3] #6 __libc_start_main in "/lib64/libc.so.6"
[3] #7 ? at ??:?
[std1708:19779:0] Caught signal 8 (Floating point exception)
==== backtrace ====
2 0x000000000005a42c mxm_handle_error() /var/tmp/OFED_topdir/BUILD/mxm-3.5.3092/src/mxm/util/debug/debug.c:641
3 0x000000000005a59c mxm_error_signal_handler() /var/tmp/OFED_topdir/BUILD/mxm-3.5.3092/src/mxm/util/debug/debug.c:616
4 0x0000000000032510 killpg() ??:0
5 0x0000000000032495 raise() ??:0
6 0x0000000000032510 killpg() ??:0
7 0x000000000018c7da _ZN4Foam11hePsiThermoINS_9psiThermoENS_11pureMixtu reINS_19sutherlandTransportINS_7species6thermoINS_ 12hConstThermoINS_10perfectGasINS_6specieEEEEENS_2 2sensibleInternalEnergyEEEEEEEE9calculateEv() ??:0
8 0x00000000002277c5 _ZN4Foam11hePsiThermoINS_9psiThermoENS_11pureMixtu reINS_19sutherlandTransportINS_7species6thermoINS_ 12hConstThermoINS_10perfectGasINS_6specieEEEEENS_2 2sensibleInternalEnergyEEEEEEEE7correctEv() ??:0
9 0x0000000000427fe7 main() ??:0
10 0x000000000001ed1d __libc_start_main() ??:0
11 0x0000000000424059 _start() ??:0
===================
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Old   April 5, 2018, 04:15
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Quote:
Originally Posted by quarkz View Post
Hi,

I got this error below when running a hypersonic flow problem. The problem has been adpted from the wedge15Ma5 example. May I know what it means?

I've tried many interpolation schemes but only upwind works. However, it is only 1st order. I hope to use other schemes which are 2nd order. What can I do to prevent divergence?

I have lowered deltaT, maxCo etc

[3] #0 Foam::error:rintStack(Foam::Ostream&) at ??:?
[3] #1 Foam::sigFpe::sigHandler(int) at ??:?
[3] #2 ? in "/lib64/libc.so.6"
[3] #3 Foam::hePsiThermo<Foam:siThermo, Foam:ureMixture<Foam::sutherlandTransport<Foam:: species::thermo<Foam::hConstThermo<Foam:erfectGa s<Foam::specie> >, Foam::sensibleInternalEnergy> > > >::calculate() at ??:?
[3] #4 Foam::hePsiThermo<Foam:siThermo, Foam:ureMixture<Foam::sutherlandTransport<Foam:: species::thermo<Foam::hConstThermo<Foam:erfectGa s<Foam::specie> >, Foam::sensibleInternalEnergy> > > >::correct() at ??:?
[3] #5 ? at ??:?
[3] #6 __libc_start_main in "/lib64/libc.so.6"
[3] #7 ? at ??:?
[std1708:19779:0] Caught signal 8 (Floating point exception)
==== backtrace ====
2 0x000000000005a42c mxm_handle_error() /var/tmp/OFED_topdir/BUILD/mxm-3.5.3092/src/mxm/util/debug/debug.c:641
3 0x000000000005a59c mxm_error_signal_handler() /var/tmp/OFED_topdir/BUILD/mxm-3.5.3092/src/mxm/util/debug/debug.c:616
4 0x0000000000032510 killpg() ??:0
5 0x0000000000032495 raise() ??:0
6 0x0000000000032510 killpg() ??:0
7 0x000000000018c7da _ZN4Foam11hePsiThermoINS_9psiThermoENS_11pureMixtu reINS_19sutherlandTransportINS_7species6thermoINS_ 12hConstThermoINS_10perfectGasINS_6specieEEEEENS_2 2sensibleInternalEnergyEEEEEEEE9calculateEv() ??:0
8 0x00000000002277c5 _ZN4Foam11hePsiThermoINS_9psiThermoENS_11pureMixtu reINS_19sutherlandTransportINS_7species6thermoINS_ 12hConstThermoINS_10perfectGasINS_6specieEEEEENS_2 2sensibleInternalEnergyEEEEEEEE7correctEv() ??:0
9 0x0000000000427fe7 main() ??:0
10 0x000000000001ed1d __libc_start_main() ??:0
11 0x0000000000424059 _start() ??:0
===================
Hi there,

Does it happen immediately after running? if so as the error states (floating point exception) can be caused by poor defined boundary/initial conditions. If it happens after some time steps you may check the errors/residuals to see what is causing this issue.

In general, if you are facing such errors in the beginning of a simulation, the best thing is to simplify the problem. You may do so by for exp. turning turbulence off, using first order Euler for ddt, turning off function objects (if there exists any) and even running in serial first instead of parallel. If the error still persists you may also use debug switches.

hope this helps...
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Old   April 5, 2018, 08:00
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Hi,

I totally agree with what einstein_zee said just before, but just to add one or two things.
You can also try to put some relaxation factors if the divergence is coming from physical parameters or also reduce the relative residual tolerance of your solvers (in fvSolution file).
One other thing could be to try to refine your mesh if these advices do not work for your case.

Cheers and good luck
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Old   April 6, 2018, 20:04
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Thanks for the answers clemerlin and einstein_zee!

My problem diverges after a short while. Anyway, I manage to get things working after changing the transport eqn from sutherland to constant, lowering CFL, and using Euler. I wonder if these changes will make the result less accurate?

Also, for high speed compressible flow, is it better to use 2nd order upwind family instead of linear for the divScheme and gradSchemes ?

Thanks
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Old   April 7, 2018, 03:18
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Another idea is to write a result at each time step. You may see then from which region the problems arise.
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Old   July 9, 2018, 01:22
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Quote:
Originally Posted by piu58 View Post
Another idea is to write a result at each time step. You may see then from which region the problems arise.
Hi Piu,

I tried this before. But strangely, I did not notice any large changes in U, p or T when I view in paraview. I can only see from the error msg that "e" diverges.
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