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-   -   Trouble with Mesh non-orthogonality (https://www.cfd-online.com/Forums/openfoam/107621-trouble-mesh-non-orthogonality.html)

mmkr825 October 2, 2012 15:48

Trouble with Mesh non-orthogonality
 
Hi Foamers,
I prepared my solver which is non-linear PDE. I am working on suspension flow (Fluid+Particles) through different geometries. When i compiled my solver then it is giving no errors, but when i run my case file by using my solver it is giving some error message.

Error message:-
Starting time loop

Time = 1nl [0 0 -1 0 0 0 0] 0.02716
DILUPBiCG: Solving for Ux, Initial residual = 1, Final residual = 4.70429e-06, No Iterations 5
DILUPBiCG: Solving for Uy, Initial residual = 0, Final residual = 0, No Iterations 0
swak4Foam: Allocating new repository for sampledGlobalVariables
#0 Foam::error::printStack(Foam::Ostream&) in "/opt/openfoam211/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#1 Foam::sigFpe::sigHandler(int) in "/opt/openfoam211/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#2 Uninterpreted:
#3 Foam::DILUPreconditioner::calcReciprocalD(Foam::Fi eld<double>&, Foam::lduMatrix const&) in "/opt/openfoam211/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#4 Foam::DILUPreconditioner::DILUPreconditioner(Foam: :lduMatrix::solver const&, Foam::dictionary const&) in "/opt/openfoam211/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#5 Foam::lduMatrix::preconditioner::addasymMatrixCons tructorToTable<Foam::DILUPreconditioner>::New(Foam ::lduMatrix::solver const&, Foam::dictionary const&) in "/opt/openfoam211/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#6 Foam::lduMatrix::preconditioner::New(Foam::lduMatr ix::solver const&, Foam::dictionary const&) in "/opt/openfoam211/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#7 Foam::PBiCG::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const in "/opt/openfoam211/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#8 Foam::fvMatrix<double>::solve(Foam::dictionary const&) in "/opt/openfoam211/platforms/linuxGccDPOpt/lib/libfiniteVolume.so"
#9 Foam::fvMatrix<double>::solve() in "/home/malli_reddy/OpenFOAM/malli_reddy-2.1.1/platforms/linuxGccDPOpt/bin/twoFoam"
#10
in "/home/malli_reddy/OpenFOAM/malli_reddy-2.1.1/platforms/linuxGccDPOpt/bin/twoFoam"
#11 __libc_start_main in "/lib/i386-linux-gnu/libc.so.6"
#12
in "/home/malli_reddy/OpenFOAM/malli_reddy-2.1.1/platforms/linuxGccDPOpt/bin/twoFoam"
Floating point exception


My governing equation involves non-linear equations. When i give good initial guess (i.e by running the case by using linear solver instead of non-linear solver at first for the guess) then the case is running properly and giving good results for simple channel flow.(in which for Mesh non-orthogonality Max: 0 average: 0)
When i repeat the above same procedure for non zero Mesh non-orthogonality then after two iterations the solution is diverging.

Please let me know what is the problem and what above error trying to explain.

Thanks
Regards
Mallikarjuna

som87 October 25, 2012 01:13

Only Ux and Uy?..You need to consider a Control Volume for OF.It appears there is some problem with the geometry specification.If you are going for solely 2D case, create a unit mesh in the z direction...

hope it helps

kmooney October 25, 2012 12:09

Quote:

Originally Posted by som87 (Post 388403)
Only Ux and Uy?..You need to consider a Control Volume for OF.It appears there is some problem with the geometry specification.If you are going for solely 2D case, create a unit mesh in the z direction...

hope it helps


If you're running a 2D case OF will only solve for the x and y components in the segregated solution so there's no problem there. If introducing mesh non-orthogonality is killing your stability, try increasing the number of nNonOrthogonalCorrectors in the /system/fvSolution dictionary. If you mesh is too skewed, however, you might be out of luck and want to try some different meshing strategies.

som87 October 25, 2012 18:00

O my......totally forgot about segregated solver situation. Thank you very much for the correction.


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