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May 5, 2013, 08:42 |
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#21 |
Senior Member
Ehsan
Join Date: Oct 2012
Location: Iran
Posts: 2,208
Rep Power: 26 |
in mutkWallFunctionFvPatchScalarField the equation uses for y-plus is related to y-star not y-plus
Code: Code:
y-star=pow(0.09,0.25)*sqr(k)*nearDist()/mu Code:
y-plus=rho*u_star*y/mu which u*=aqrt(taw_w/rho) in the code of mut : Code: Code:
forAll(mutw, faceI) { label faceCellI = patch().faceCells()[faceI]; scalar yPlus = Cmu25*y[faceI]*sqrt(k[faceCellI])/(muw[faceI]/rhow[faceI]); if (yPlus > yPlusLam_) { mutw[faceI] = muw[faceI]*(yPlus*kappa_/log(E_*yPlus) - 1); } }
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May 4, 2016, 05:15 |
Correction necessary on Niklas's code
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#22 |
New Member
eu sou cfd
Join Date: Jun 2012
Location: Brazil
Posts: 18
Rep Power: 13 |
I believe I am very late to the party. I am currently using the OpenFOAM 2.4.0 and I have to say that they still have not made any changes to the code, even though I believe it would not be a involve a lot of coding. There was a post on the official openFOAM page, in case you might want to have a look, here it is http://www.openfoam.org/mantisbt/view.php?id=835
Well i was using the code Niklas had made, but I believe it requires a correction. Of course it needed to be edited slightly for the OpenFOAM 2.4 but that is not the correction I am talking about. When it calculates the sqrt(viscosity*gradient of velocity), it has to consider the sum of kinematic viscosity+turbulent viscosity , but he has only used the turbulent viscosity (mut.boundaryField()[patchi]). Practically, the turbulent viscoisty can be ignored and we are only left with the kinematic viscosisty. Very close to the wall i.e y+<3, the turbulent viscosity is negligible since it lies in the viscous laminar sub layer where there are negligible turbulent effects. The line I am talking about would be 3rd in the code attached which is from his Niklas's code. Code:
yPlus.boundaryField()[patchi] = y[patchi] * sqrt ( mut.boundaryField()[patchi] * mag(U.boundaryField()[patchi].snGrad()) / rho.boundaryField()[patchi] ) / (RASModel->mu().boundaryField()[patchi] /rho.boundaryField()[patchi]); Last edited by vikramaditya91; May 4, 2016 at 06:38. Reason: Grammatik |
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