Ustar and Atmospheric Boundary Layer
I was trying to use the ABL condition present in the turbineSitting tutorial in other simulation.
However I am wondering how is fixed the value of Ustar in this tutorial?
From what I know: Ustar = sqrt(Tau / rho) with Tau being the wall shear stress. The problem is this Tau is normally computed as: Tau = mu*dU/dz and I can only know the du/dz once I have done the computation.
So I have the felling that I am turning around and missing something.
Could somebody tell me how to know this value before doing the computation or advise me on how to proceed?
Ok, so I did some more testing and this value of U* does not seem to be used.
I tried to do the computation by commenting the line, and by changing U* of 0.82, 5 and even 10, and I get the same result at the end.
Then I looked in the code "atmBoundaryLayerInletVelocityFvPatchVectorField.C " and I saw the following lines:
and apparently it is recomputed afterwards:
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