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Flow instability and crash

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Old   August 18, 2014, 13:47
Default Flow instability in the mesh bounds
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Jefferson Vieira
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Hi all,

I'm running a simulation with an airfoil in transonic conditions. At some point in the simulation, the bow shock reaches the top and bottom bounds of the mesh and this causes an instability that further makes the solver crash.

Here follows the exit message:
Code:
--> FOAM FATAL ERROR: 
Maximum number of iterations exceeded

    From function thermo<Thermo, Type>::T(scalar f, scalar T0, scalar (thermo<Thermo, Type>::*F)(const scalar) const, scalar (thermo<Thermo, Type>::*dFdT)(const scalar) const, scalar (thermo<Thermo, Type>::*limit)(const scalar) const) const
    in file /home/opencfd/OpenFOAM/OpenFOAM-2.3.0/src/thermophysicalModels/specie/lnInclude/thermoI.H at line 76.

FOAM aborting

#0  Foam::error::printStack(Foam::Ostream&) at ??:?
#1  Foam::error::abort() at ??:?
#2  Foam::species::thermo<Foam::hConstThermo<Foam::perfectGas<Foam::specie> >, Foam::sensibleInternalEnergy>::TEs(double, double, double) const at ??:?
#3  Foam::hePsiThermo<Foam::psiThermo, Foam::pureMixture<Foam::constTransport<Foam::species::thermo<Foam::hConstThermo<Foam::perfectGas<Foam::specie> >, Foam::sensibleInternalEnergy> > > >::calculate() at ??:?
#4  Foam::hePsiThermo<Foam::psiThermo, Foam::pureMixture<Foam::constTransport<Foam::species::thermo<Foam::hConstThermo<Foam::perfectGas<Foam::specie> >, Foam::sensibleInternalEnergy> > > >::correct() at ??:?
#5  
 at ??:?
#6  __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#7  
 at ??:?
Aborted (core dumped)
Attached follows the images of the instabilities.

Initially I thought that it would be due to the coarse mesh at the bounds, but then I refined it and the problem persists.

Does anyone have any idea of what is happening?

Thanks in advance,
Jefferson Vieira
Attached Images
File Type: jpg Simulation Ma 0.8 a1.5_1.jpg (42.5 KB, 23 views)
File Type: jpg Simulation Ma 0.8 a1.5_2.jpg (43.3 KB, 20 views)
File Type: jpg Simulation Ma 0.8 a1.5_3.jpg (43.6 KB, 18 views)
File Type: jpg Simulation Ma 0.8 a1.5_4.jpg (43.1 KB, 14 views)

Last edited by Jefferson_dhv; August 18, 2014 at 17:53.
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Old   August 21, 2014, 09:45
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Jefferson Vieira
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I have find out that the problem is most probably due to the boundary conditions in the top and bottom bounds. Initially these patches had the same BC's as the inlet, that is fixedValue for both velocity and pressure. Afterwards I changed the BC's in these patches to solve it, but until now I've got no luck. I've tried freestream, slip, zeroGradient and outletInlet BC's for velocity, maintaining fixedValue for pressure, except for freestream.

So I ask if any of you have an idea on how I could set these BC's to fix it.

Thanks in advance,
Jefferson Vieira
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airfoil, instability, transonic

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