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#1 |
Member
Patrick Bourdin
Join Date: Mar 2009
Posts: 40
Rep Power: 17 ![]() |
one question about the way the viscous force is computed in turbulentForceAndTorqueFunctionObject.C:
// Viscous component viscousForces[patchI] = gSum ( -nuEff.boundaryField()[curPatch]* U.boundaryField()[curPatch].snGrad()* mesh.magSf().boundaryField()[curPatch] ); This is only valid in regions where the velocity field is more or less linear (snGrad being approximated by a one sided finite difference if I am not mistaken). In other words, for models with wall functions (log law), the above formulation will give incorrect viscous force estimates at the wall. Am I correct? |
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#2 |
Member
Sung-Eun Kim
Join Date: Mar 2009
Posts: 76
Rep Power: 17 ![]() |
I've also wondered about this and haven;t had time to look into the code. If the slip velocity (extrapolated using the wall-law) is somehow patched on the wall faces and the consistent eddy viscosity is used, the aboce expression should give correct wall-shear.
I'm not sure this is the way the OF works. |
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#3 |
Senior Member
Eugene de Villiers
Join Date: Mar 2009
Posts: 725
Rep Power: 21 ![]() |
I am not familiar with this function object (I guess it does the same as my liftDrag function object), but I can confirm that boundary values of nuEff on a wall will include the effects of wall functions if they are present in the turbulence model.
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