Nonlinear k epsilon Shih Model
Hallo Foamers!
Does anybody know a reference where I can find the derivation of the Nonlinear k e Shih model? Cheers |
Does really nobody knows a reference, at least one? HELP
|
Does really nobody knows a reference, at least one? HELP
|
Hi Claus,
the paper you are searching for can be found at the NASA pages. There you have access to a lot of other papers of Shih: http://ntrs.nasa.gov/search.jsp?R=35...%257c1%26N%3D0 Best regards, Olli |
Hi,
have you simulated successful using this turbulence-model? I have problems near walls (U isn't zero orthogonal to the wall in the nearwall-part even in channel-flows). Regards Thomas |
Hi,
yes I'm using this turbulence model for simulating swirling flows. For this purpose it seems to be perfect. I haven't discovered any problems until know. Olli |
Hi,
I have velocities out of the wall. I have described this in a posting here in the forum. http://www.cfd-online.com/Forums/ope...inearshih.html But if I'm using a very fine mesh (y+ < 0.4) the results are better. So the solution has a mesh-dependence. Maybe it's caused by the fvschemss are the solvers for p,U,k... I have tried different ones without success. Could you maybe show your fvschemes and the fvSolution-data, please? Thanks and regards, Thomas |
Hi Thomas,
a y+ of less than 0.4 seems to be a sufficient fine mesh. Nevertheless, are k-epsilon models known for their bad boundary layer behaviour. Therefore this model uses an boundary layer model in the near wall region. I can look up how it is set up. If the results have a mesh-dependence you should probably do a grid study :-( An other way would be to use an much coarser mesh, if boundary layers are not prior-ranking. Olli fvSchemes: ----------------------------------------------------------------- ddtSchemes { default steadyState; } gradSchemes { default Gauss linear; grad(p) Gauss linear; grad(U) Gauss linear; // grad(U) cellLimited Gauss linear 1; } divSchemes { default none; div(phi,U) Gauss linearUpwindV Gauss linear; div(phi,k) Gauss upwind; div(phi,omega) Gauss upwind; div((nuEff*dev(grad(U).T()))) Gauss linear; div(nonlinearStress) Gauss linear; div(phi,epsilon) Gauss upwind; div(phi,R) Gauss upwind; div(R) Gauss linear; div(phi,nuTilda) Gauss upwind; } laplacianSchemes { default Gauss linear corrected; // default Gauss linear limited 0.5; // default Gauss linear limited 0.333; laplacian(nuEff,U) Gauss linear corrected; laplacian((1|A(U)),p) Gauss linear corrected; laplacian(DkEff,k) Gauss linear corrected; laplacian(DepsilonEff,epsilon) Gauss linear corrected; laplacian(DREff,R) Gauss linear corrected; laplacian(DnuTildaEff,nuTilda) Gauss linear corrected; } interpolationSchemes { default linear; interpolate(U) linear; } snGradSchemes { default corrected; } fluxRequired { default no; p; } fvSolution: ------------------------------------------------------- solvers { p { solver GAMG; preconditioner FDIC; mergeLevels 1; smoother GaussSeidel; agglomerator faceAreaPair; nCellsInCoarsestLevel 100; tolerance 1e-06; relTol 0.01; } U { solver GAMG; preconditioner DILU; tolerance 1e-05; relTol 0.1; mergeLevels 1; smoother GaussSeidel; agglomerator faceAreaPair; nCellsInCoarsestLevel 100; tolerance 1e-05; relTol 0; } k { solver PBiCG; preconditioner DILU; tolerance 1e-05; relTol 0.1; } epsilon { solver PBiCG; preconditioner DILU; tolerance 1e-05; relTol 0.1; } R { solver PBiCG; preconditioner DILU; tolerance 1e-05; relTol 0.1; } nuTilda { solver PBiCG; preconditioner DILU; tolerance 1e-05; relTol 0.1; } } SIMPLE { nNonOrthogonalCorrectors 0; } relaxationFactors { p 0.2; U 0.5; k 0.7; epsilon 0.7; R 0.7; nuTilda 0.7; } |
Hi,
thank you very much. I have simulated using your given condition, but the velocities didn't get better. Have you ever simulated a non-swirling flow using this model? Regards Thomas |
Hi,
no, I never simulated a non-swirling case with this model. I just used the model because all other models either crashed or over predicted the axial velocity. I looked at your other post and really have no idea what is going wrong there. Olli |
Update for link to Shih et al. 1993
Hey all, I tried Moelfus' link to the paper, but it looks as if NASA changed it since it could not be found at that address. The correct one is now...
https://ntrs.nasa.gov/archive/nasa/c...9930007407.pdf. |
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