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-   -   boundary condition porblem.. (http://www.cfd-online.com/Forums/openfoam-solving/124798-boundary-condition-porblem.html)

izna October 13, 2013 13:09

boundary condition porblem..
 
HI Julienn

thanks for taking the time and check my case..
for starters i had already try with symmetryPlane and below was my error

Quote:


Time = 35

DILUPBiCG: Solving for Ux, Initial residual = 0.999998272593, Final residual = 0.0518215801919, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 0.999998558302, Final residual = 0.0518147902953, No Iterations 1
#0 Foam::error::printStack(Foam::Ostream&) in "/opt/openfoam221/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#1 Foam::sigFpe::sigHandler(int) in "/opt/openfoam221/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#2 Uninterpreted:
#3 Foam::DICPreconditioner::calcReciprocalD(Foam::Fie ld<double>&, Foam::lduMatrix const&) in "/opt/openfoam221/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#4 Foam::DICPreconditioner::DICPreconditioner(Foam::l duMatrix::solver const&, Foam::dictionary const&) in "/opt/openfoam221/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#5 Foam::lduMatrix::preconditioner::addsymMatrixConst ructorToTable<Foam::DICPreconditioner>::New(Foam:: lduMatrix::solver const&, Foam::dictionary const&) in "/opt/openfoam221/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#6 Foam::lduMatrix::preconditioner::New(Foam::lduMatr ix::solver const&, Foam::dictionary const&) in "/opt/openfoam221/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#7 Foam::PCG::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const in "/opt/openfoam221/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#8 Foam::fvMatrix<double>::solveSegregated(Foam::dict ionary const&) in "/opt/openfoam221/platforms/linuxGccDPOpt/lib/libfiniteVolume.so"
#9 Foam::fvMatrix<double>::solve(Foam::dictionary const&) in "/opt/openfoam221/platforms/linuxGccDPOpt/bin/simpleFoam"
#10
in "/opt/openfoam221/platforms/linuxGccDPOpt/bin/simpleFoam"
#11 __libc_start_main in "/lib/i386-linux-gnu/libc.so.6"
#12
in "/opt/openfoam221/platforms/linuxGccDPOpt/bin/simpleFoam"
Floating point exception (core dumped)

that is why i was so desperate and has sent you my case...:(
I hope you be able to help...:( :(

julien.decharentenay October 13, 2013 19:47

I had a look at your case and tried to run a few sims.

My take is that the mesh is probably the root of the issue. I tried to take things away:
- turn turbulence off;
- use upwind scheme;
- reduce residuals;
- use a potentialFoam solution;
- change the outlet boundary conditions;
- tighten solver residuals.

The following picture shows the non-physical spike of velocity after as little as 10 iterations. Sorry, but I can't help further.
https://dl.dropboxusercontent.com/u/...e-14102013.png

izna October 13, 2013 19:52

hello Julien..

First of ALl thanks a lot for the useful and intelligent pointers you gave to me..

As wih simpleFoam its not working at all.. I have used pisoFOam and still it not work.

But with pisoFoam i include the boundary cond of symmetryPlane.. so lo and behold... the FLow is being as i wanted!!!

Thanks heapsssss.....

But with pisoFoam, it takes along timeeeee to finish iterating and acheive convergence..

i am now at 20319 second and its sill going strong in iteration.. But at least its giving the required results..

julien.decharentenay October 14, 2013 01:31

Following your post: you may want to try changing:

Code:

      nNonOrthogonalCorrectors 0;
to:

Code:

      nNonOrthogonalCorrectors 5;
in the fvSolution scheme when using simpleFoam.

izna October 14, 2013 01:33

thanks am trying it right away..

I am obtaining superb resutls with pisofoam. but WHY DOES IT TAKE SOO MUCH TIME TO ITERATE???


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