[mart.hein]

Hello everybody,

I want to implement a boundary condition, where I can define the shear stress at a wall. First I tried to adopt the mutWallFunction for my purpose and modified it to calculate the turbulent viscosity as follows

 mut = tauWall / gradU - mu

where tauWall is my specified wall shear stress, gradU the velocity gradient normal to the wall and mu the molecular viscosity.

Unfortunately this only works well for coarse meshes. In other cases the velocity gradient becomes to large and the turbulent viscosity gets negative.

Is there a better way to implement such a boundary condition?

Thanks for your help!

Regards

Martin

[eugene]

You could create a specific wall boundary condition for U that overrides the snGrad fvPatchField function so as to provide a wall velocity gradient equal to: gradU = tauw / nutw