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what is correct boundary condition for K-w sst model at y+<1? |
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August 4, 2013, 14:35 |
what is correct boundary condition for K-w sst model at y+<1?
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#1 |
Senior Member
Join Date: Jun 2011
Posts: 163
Rep Power: 14 |
Hi
I found some thread about k-w sst boundary conditions unfortunately they are not clear in low y+ please let me know what is correct boundary conditions for k, w and nut for y+<5 Best Regards |
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August 4, 2013, 15:42 |
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#2 |
New Member
Andre Weiner
Join Date: Aug 2012
Posts: 29
Rep Power: 13 |
Hello!
omega: Menter's automatic wall funcion works for all parts of the momentum boundary layer, in openfoam it's the omegaWallFunction http://www.cfd-online.com/Wiki/Near-...k-omega_models or you use the solution for the viscos sublayer to set the boundary value http://turbmodels.larc.nasa.gov/sst.html (there is an equation for omega_wall) for y^+<5 both give the same results k: fixed value 0 or zero gradient if you look at same results for k near the wall (from other simulations for example), you will see that both are valid (again for y^+<5) nut: calculated or fixed value 0 or nutLowReWallFunction (sets the value to zero and provides a function for calculating y^+ which is needed for the yPlusRAS tool) This is what i tried so far and it worked for mi :-) Best regards, Andre |
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August 5, 2013, 03:51 |
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#3 | |
Senior Member
Join Date: Jun 2011
Posts: 163
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Quote:
what function should be set for calculating y+ ? and how set it ? can you attached an example for k,w,nut (initial file at folder 0)? Best Regards |
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August 5, 2013, 10:29 |
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#4 |
Senior Member
Joachim
Join Date: Mar 2012
Location: Paris, France
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Actually, I think that nutLowReWallFunction is a wall function for low-Re turbulence models. If you use LaunderSharmaKE and have y+ ~ 60, you can use it for example.
Also, try using 1e-9 (or any small value) rather than 0 when imposing the BC. Good luck! |
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August 5, 2013, 14:17 |
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#5 |
New Member
Andre Weiner
Join Date: Aug 2012
Posts: 29
Rep Power: 13 |
for k:
Code:
myWall { type zeroGradient; } // or myWall { type fixedValue; value uniform 0; } Code:
myWall { type omegaWallFunction; } Code:
myWall { type fixedValue; value uniform 0; } // or myWall { type calculated; value uniform 0; // optional value entry } // what i prefer myPatch { type nutLowReWallFunction; } it sets nut to zero: Code:
tmp<scalarField> nutLowReWallFunctionFvPatchScalarField::calcNut() const { return tmp<scalarField>(new scalarField(patch().size(), 0.0)); } Code:
tmp<scalarField> nutLowReWallFunctionFvPatchScalarField::yPlus() const { .... return y*sqrt(nuw*mag(Uw.snGrad()))/nuw; } |
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