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Old   March 5, 2010, 02:15
Question Friction Velocity
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Pooven
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Hi there,

I don't have a CFD background so I'm not sure if what I've done is correct; I was hoping for some clarity... I want to define a drag force at the floor of my simulation. I do this in the /0/U file:
In the boundaryField sub-dictionary, in the floor wall sub-dictionary I calculate the drag force using by using u_* = k u_k/ln(h/z_0).
I think that the drag force in this case is the friction velocity?

I have to represent the friction velocity as a vector so I convert it using sin(x) * u_* and cos(x) * u_* where x is in the opposite direction of the flow (though I don't think it makes a difference?) and the z component of the vector is set to 0.

Am I totally off?

Kind regards
Pooven
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