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February 23, 2017, 11:53 |
icoFoam pipe case no flow / divergence
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#1 |
New Member
Jeremy
Join Date: May 2016
Posts: 17
Rep Power: 9 |
Hi everyone,
I am trying to run my first case built from scratch and have run into a few problems that require some feedback. I created a 3D pipe in AutoCAD, used snappyHexMesh, and now I want to model laminar, incompressible flow through the pipe. The issues that I'm facing right now are that the Courant number blows up. I can get the solution to converge when deltat=0.5, but anything smaller than that crashes. Here is the geometry: checkMesh shows no problems: checkMesh Here are the solver/schemes set up files: fvSchemes fvSolution Here is the log file from running icoFoam (deltat = 0.05): icoFoam.log Here is some output from the terminal: Code:
Time = 0.005 Courant Number mean: 0.000628106 max: 0.056034 smoothSolver: Solving for Ux, Initial residual = 1, Final residual = 9.66498e-06, No Iterations 198 smoothSolver: Solving for Uy, Initial residual = 1, Final residual = 9.72787e-06, No Iterations 208 smoothSolver: Solving for Uz, Initial residual = 1, Final residual = 9.86911e-06, No Iterations 418 DICPCG: Solving for p, Initial residual = 1, Final residual = 0.0312899, No Iterations 23 time step continuity errors : sum local = 0.80011, global = -0.00335702, cumulative = -0.00335702 DICPCG: Solving for p, Initial residual = 0.0978647, Final residual = 7.77585e-07, No Iterations 39 time step continuity errors : sum local = 0.000242407, global = 4.4505e-07, cumulative = -0.00335657 ExecutionTime = 1.09 s ClockTime = 2 s Time = 0.01 Courant Number mean: 51.1202 max: 1136.82 smoothSolver: Solving for Ux, Initial residual = 0.615202, Final residual = 5567.72, No Iterations 1000 smoothSolver: Solving for Uy, Initial residual = 0.615546, Final residual = 5612.95, No Iterations 1000 smoothSolver: Solving for Uz, Initial residual = 0.689541, Final residual = 41639.2, No Iterations 1000 DICPCG: Solving for p, Initial residual = 1, Final residual = 0.0441477, No Iterations 80 time step continuity errors : sum local = 2.68406e+07, global = -27973.8, cumulative = -27973.8 DICPCG: Solving for p, Initial residual = 0.000279914, Final residual = 7.89735e-07, No Iterations 86 time step continuity errors : sum local = 1.19323e+07, global = 692.433, cumulative = -27281.4 ExecutionTime = 4.9 s ClockTime = 5 s Time = 0.015 Courant Number mean: 9.89028e+09 max: 8.94025e+11 smoothSolver: Solving for Ux, Initial residual = 0.849814, Final residual = 1.14434e+06, No Iterations 1000 smoothSolver: Solving for Uy, Initial residual = 0.850397, Final residual = 26031.3, No Iterations 1000 smoothSolver: Solving for Uz, Initial residual = 0.807674, Final residual = 4.24709e+06, No Iterations 1000 DICPCG: Solving for p, Initial residual = 1, Final residual = 0.0325397, No Iterations 61 time step continuity errors : sum local = 2.2162e+17, global = 6.05571e+16, cumulative = 6.05571e+16 DICPCG: Solving for p, Initial residual = 0.0024243, Final residual = 5.44929e-07, No Iterations 5 time step continuity errors : sum local = 3.98111e+24, global = 9.98492e+22, cumulative = 9.98493e+22 ExecutionTime = 8.69 s ClockTime = 9 s Time = 0.02 Courant Number mean: 4.77595e+26 max: 3.64552e+31 #0 Foam::error::printStack(Foam::Ostream&) at ??:? #1 Foam::sigFpe::sigHandler(int) at ??:? #2 ? in "/lib/x86_64-linux-gnu/libc.so.6" #3 Foam::symGaussSeidelSmoother::smooth(Foam::word const&, Foam::Field<double>&, Foam::lduMatrix const&, Foam::Field<double> const&, Foam::FieldField<Foam::Field, double> const&, Foam::UPtrList<Foam::lduInterfaceField const> const&, unsigned char, int) at ??:? #4 Foam::symGaussSeidelSmoother::smooth(Foam::Field<double>&, Foam::Field<double> const&, unsigned char, int) const at ??:? #5 Foam::smoothSolver::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const at ??:? #6 ? at ??:? #7 ? at ??:? #8 ? at ??:? #9 ? at ??:? #10 __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6" #11 ? at ??:? Floating point exception The full case is contained here: pipeTest2 case Please help! |
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February 23, 2017, 14:05 |
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#2 |
Member
Joshua
Join Date: Dec 2016
Location: St. Louis, Missouri
Posts: 91
Rep Power: 9 |
j_moulton,
icoFoam is a transient solver with a fixed time step. To accommodate Courant number issues all you can do is decrease your time step or create a coarser mesh. Try dropping your deltaT to 0.005 or even 0.0005. Best Regards, Joshua |
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