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February 25, 2010, 11:16 
Nonlinear k epsilon Shih Model

#1 
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Claus Meister
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Hallo Foamers!
Does anybody know a reference where I can find the derivation of the Nonlinear k e Shih model? Cheers 

May 21, 2010, 02:39 

#2 
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Claus Meister
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Does really nobody knows a reference, at least one? HELP


May 21, 2010, 03:05 

#3 
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Claus Meister
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Does really nobody knows a reference, at least one? HELP


August 24, 2010, 03:28 

#4 
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Olli
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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 

August 25, 2010, 09:29 

#5 
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Hi,
have you simulated successful using this turbulencemodel? I have problems near walls (U isn't zero orthogonal to the wall in the nearwallpart even in channelflows). Regards Thomas 

August 26, 2010, 04:29 

#6 
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Olli
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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 

August 26, 2010, 05:11 

#7 
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Hi,
I have velocities out of the wall. I have described this in a posting here in the forum. Nonlinear turbulence model NonlinearShih But if I'm using a very fine mesh (y+ < 0.4) the results are better. So the solution has a meshdependence. 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 fvSolutiondata, please? Thanks and regards, Thomas 

August 27, 2010, 06:32 

#8 
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Olli
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Hi Thomas,
a y+ of less than 0.4 seems to be a sufficient fine mesh. Nevertheless, are kepsilon 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 meshdependence you should probably do a grid study :( An other way would be to use an much coarser mesh, if boundary layers are not priorranking. 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((1A(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 1e06; relTol 0.01; } U { solver GAMG; preconditioner DILU; tolerance 1e05; relTol 0.1; mergeLevels 1; smoother GaussSeidel; agglomerator faceAreaPair; nCellsInCoarsestLevel 100; tolerance 1e05; relTol 0; } k { solver PBiCG; preconditioner DILU; tolerance 1e05; relTol 0.1; } epsilon { solver PBiCG; preconditioner DILU; tolerance 1e05; relTol 0.1; } R { solver PBiCG; preconditioner DILU; tolerance 1e05; relTol 0.1; } nuTilda { solver PBiCG; preconditioner DILU; tolerance 1e05; 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; } 

August 27, 2010, 11:05 

#9 
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Hi,
thank you very much. I have simulated using your given condition, but the velocities didn't get better. Have you ever simulated a nonswirling flow using this model? Regards Thomas 

August 30, 2010, 09:37 

#10 
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Olli
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Hi,
no, I never simulated a nonswirling 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 

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