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Laminar compressible flow trough a venturi-tube |
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June 14, 2015, 05:48 |
Laminar compressible flow trough a venturi-tube
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#1 |
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Ruben Stap
Join Date: Jun 2015
Posts: 3
Rep Power: 10 |
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). -------------------------------------------------------------------------- Kind-regards, Ruben |
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June 15, 2015, 04:51 |
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#2 |
New Member
Babak Gholami
Join Date: Jul 2014
Posts: 3
Rep Power: 11 |
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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