# limitation of k and epsilon

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 November 7, 2010, 02:20 limitation of k and epsilon #1 Member   Mohammad.R.Shetab Join Date: Jul 2010 Posts: 49 Rep Power: 9 Dear Foamers I'm modeling a centrifugal fan with MRFSimpleFoam and kEpsilon model, and I want to limit k and epsilon between 1e-10 and 30. How can I do that. I read userGuide and so I managed below fvSchemes dictionary, but it didn't work. How can I do that?! Anybody knows?!!!! ddtSchemes { default steadyState; } gradSchemes { default cellLimited Gauss linear 1; grad(p) cellLimited Gauss linear 1; grad(U) cellLimited Gauss linear 1; //grad(k) Gauss limitedVanLeer phi 1e-10 30; //grad(epsilon) Gauss limitedVanLeer phi 1e-10 30; } divSchemes { default none; div(phi,U) Gauss linearUpwindV cellMDLimited Gauss linear 1; //div(phi,k) Gauss upwind phi; div(phi,k) Gauss limitedVanLeer 1e-10 30; //div(phi,k) Gauss linearUpwind cellLimited Gauss linear 1; //div(phi,epsilon) Gauss upwind phi; div(phi,epsilon) Gauss limitedVanLeer 1e-10 30; //div(phi,epsilon) Gauss linearUpwind cellLimited Gauss linear 1; div((nuEff*dev(grad(U).T()))) Gauss linear; } laplacianSchemes { default none; laplacian(nuEff,U) Gauss upwind phi limited 1; laplacian((1|A(U)),p) Gauss upwind phi limited 1; laplacian(DkEff,k) Gauss limitedVanLeer phi 1e-10 30 limited 1; laplacian(DepsilonEff,epsilon) Gauss limitedVanLeer phi 1e-10 30 limited 1; } interpolationSchemes { default upwind phi; interpolate(epsilon) limitedLinear 1e-10 30; interpolate(k) limitedLinear 1e-10 30; } snGradSchemes { default bounded; } fluxRequired { default no; p ; } // ************************************************** *********************** // Best regards Mohammadreza

 November 7, 2010, 08:28 #2 Senior Member   Nima Samkhaniani Join Date: Sep 2009 Location: Tehran, Iran Posts: 1,240 Blog Entries: 1 Rep Power: 18 i dont know any way from Dic u can limit ur k or e but in source code you can add something like that: k =min(max(k,scalar(0)),scalar(30))

 November 7, 2010, 08:58 min-max #3 Member   Mohammad.R.Shetab Join Date: Jul 2010 Posts: 49 Rep Power: 9 Dear Nima Thank you for your reply. I will test it. The only question here is I should write for term k like this? k=max(k,scalar(0)); k=min(k,scalar(30)); or like what you wrote: k=min(max(k,scalar(0),scalar(30))) they have the same meaning or not?!!! Thank you again Mohammadreza

 November 7, 2010, 11:00 #4 Senior Member   Nima Samkhaniani Join Date: Sep 2009 Location: Tehran, Iran Posts: 1,240 Blog Entries: 1 Rep Power: 18 they have the same meaning just its somehow more beautiful expression and if you dont like to change the main variable you can define new variable for example kLimited then : volScalarField kLimited = min(max(k,scalar(0)),scalar(30)) then use this limited version in ur calculation

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