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Laminar compressible flow trough a venturi-tube

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Old   June 14, 2015, 05:48
Default Laminar compressible flow trough a venturi-tube
  #1
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Ruben Stap
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Hello everyone,
I've got a venturi tube in which I'm running a Laminar Compressible flow simulation in Simscale (which uses openfoam) of carbon dioxide flowing trough.

The inlet is located on the left-hand side of the picture and the outlet is located on the right side of the picture.
My boundary conditions are as follows:
Inlet:
Vx=100
Vy=0
Vz=0
P=set gradiënt to zero
T=293
Outlet:
V=Set gardiënt to zero
P=100000
T=Set gradiënt to zero
Dynamic viscocity = calculated
Dynamic viscocity=0.000014
For the wall i'm using a wall boundary condition which has a no-slip condition for velocity and set gradient to zero for temperature.
The problem is, that everytime I make the pressure in the initial conditions higher then the pressure of the outlet, I get the following error:
Code:
DILUPBiCG: Solving for Ux, Initial residual = 1, Final residual = 0.00127224785092, No Iterations 2
DILUPBiCG: Solving for Uy, Initial residual = 1, Final residual = 0.00504466914548, No Iterations 2
DILUPBiCG: Solving for Uz, Initial residual = 1, Final residual = 0.00614310410684, No Iterations 2
--> FOAM Warning :
From function gaussConvectionScheme
in file finiteVolume/convectionSchemes/gaussConvectionScheme/gaussConvectionScheme.H at line 123
Reading "system/fvSchemes.divSchemes.div(phi,K)" at line 18
Unbounded 'Gauss' div scheme used in steady-state solver, use 'bounded Gauss' to ensure boundedness.
To remove this warning switch off 'boundedGauss' in "
--> FOAM Warning :
From function gaussConvectionScheme
in file finiteVolume/convectionSchemes/gaussConvectionScheme/gaussConvectionScheme.H at line 123
Reading "system/fvSchemes.divSchemes.div(phi,h)" at line 15
Unbounded 'Gauss' div scheme used in steady-state solver, use 'bounded Gauss' to ensure boundedness.
To remove this warning switch off 'boundedGauss' in "
DILUPBiCG: Solving for h, Initial residual = 1, Final residual = 0.000945621543136, No Iterations 2
DICPCG: Solving for p, Initial residual = 0.999999999996, Final residual = 0.0376026758747, No Iterations 1001
time step continuity errors : sum local = 0.0800376014586, global = 0.00387144739956, cumulative = 0.00387144739956
rho max/min : 0.5 0.5
ExecutionTime = 8.82 s ClockTime = 9 s
Time = 0.01
DILUPBiCG: Solving for Ux, Initial residual = 0.0898757338962, Final residual = 3.2859857618e-05, No Iterations 4
DILUPBiCG: Solving for Uy, Initial residual = 0.400032480512, Final residual = 0.00254776037522, No Iterations 2
DILUPBiCG: Solving for Uz, Initial residual = 0.395296372538, Final residual = 0.00227531217043, No Iterations 2
--> FOAM Warning :
From function gaussConvectionScheme
in file finiteVolume/convectionSchemes/gaussConvectionScheme/gaussConvectionScheme.H at line 123
Reading "system/fvSchemes.divSchemes.div(phi,K)" at line 18
Unbounded 'Gauss' div scheme used in steady-state solver, use 'bounded Gauss' to ensure boundedness.
To remove this warning switch off 'boundedGauss' in "
--> FOAM Warning :
From function gaussConvectionScheme
in file finiteVolume/convectionSchemes/gaussConvectionScheme/gaussConvectionScheme.H at line 123
Reading "system/fvSchemes.divSchemes.div(phi,h)" at line 15
Unbounded 'Gauss' div scheme used in steady-state solver, use 'bounded Gauss' to ensure boundedness.
To remove this warning switch off 'boundedGauss' in "
DILUPBiCG: Solving for h, Initial residual = 0.335547239474, Final residual = 0.000568389685507, No Iterations 3
[2]
[2]
[2] --> FOAM FATAL ERROR:
[2] Maximum number of iterations exceeded
[2]
[2] 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
[2] in file at line 76.
[2]
FOAM parallel run aborting
[2]
[2] #0 Foam::error::printStack(Foam::Ostream&) at ??:?
[2] #1 Foam::error::abort() at ??:?
[2] #2 Foam::species::thermo<Foam::hConstThermo<Foam::perfectGas<Foam::specie> >, Foam::sensibleEnthalpy>::THs(double, double, double) const at ??:?
[2] #3 Foam::hePsiThermo<Foam::psiThermo, Foam::pureMixture<Foam::constTransport<Foam::species::thermo<Foam::hConstThermo<Foam::perfectGas<Foam::specie> >, Foam::sensibleEnthalpy> > > >::calculate() at ??:?
[2] #4 Foam::hePsiThermo<Foam::psiThermo, Foam::pureMixture<Foam::constTransport<Foam::species::thermo<Foam::hConstThermo<Foam::perfectGas<Foam::specie> >, Foam::sensibleEnthalpy> > > >::correct() at ??:?
[2] #5
[2] at ??:?
[2] #6 __libc_start_main in "
[2] #7
[2] at ??:?
--------------------------------------------------------------------------
MPI_ABORT was invoked on rank 2 in communicator MPI_COMM_WORLD
with errorcode 1.
NOTE: invoking MPI_ABORT causes Open MPI to kill all MPI processes.
You may or may not see output from other processes, depending on
exactly when Open MPI kills them.
--------------------------------------------------------------------------
--------------------------------------------------------------------------
mpirun has exited due to process rank 2 with on
node exiting improperly. There are two reasons this could occur:
1. this process did not call "init" before exiting, but others in
the job did. This can cause a job to hang indefinitely while it waits
for all processes to call "init". By rule, if one process calls "init",
then ALL processes must call "init" prior to termination.
2. this process called "init", but exited without calling "finalize".
By rule, all processes that call "init" MUST call "finalize" prior to
exiting or it will be considered an "abnormal termination"
This may have caused other processes in the application to be
terminated by signals sent by mpirun (as reported here).
--------------------------------------------------------------------------
When not, the simulation runs just fine. Does anyone know how this can happen.
Kind-regards,
Ruben
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Old   June 15, 2015, 04:51
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  #2
joi
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Babak Gholami
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Hi Ruben,

I'm glad to hear you're using SimScale for your simulation.

The reason for this error is that temperature has increased beyond the maximum allowed for calculating properties of the fluid. This means your solution is diverging (unless you want to reach such high temperatures which is a different story).

Compressible simulations are very sensitive in general. Therefore, if for any specific reason you want to keep the initial pressure higher than the outlet, I would suggest considering these:

- Avoid using high-order schemes.
- As the log suggests, use bounded schemes for divergence terms. It would be a good idea to use something like a cell-limited scheme for gradient terms as well.
- Using GAMG and smooth solvers could help.
- Tighten up your residual controls.
- Use smaller relaxation factors.

All in all, it is probably a good idea to be a little conservative when it comes to compressible simulations. Once you identified the critical settings, you can play around with the rest.

I hope this helps
Babak

--
Babak Gholami
Engineer at SimScale
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