Extapolation of forces with wall laws.
 

Hi. Doe's anybody know if/how it is possible to extraplate the shear forces from the values obtained with k-epsilon wall laws in order to get more accurate lift and drag force calculations.

That is, I want to be able to obtain values of the forces directly at the walls even though I have used wall laws and thus don't have access to the values at the walls.

Re: Extapolation of forces with wall laws.
 

I guess the friction velocity of the wall law can give the wall shear.

Re: Extapolation of forces with wall laws.
 

Well as I see it by using the friction velocity to get the shear stress you only get the value at y+=50 or so, and not at the actual wall where y+=0. Maybee there's not much difference, anybody that has experience with this?

Re: Extapolation of forces with wall laws.
 

u+ = sqrt(Tau_wall/rho) where Tau_wall is the shear at the wall.

Since you have y+ at point y, it comes :

nu*y+/y = u+ = sqrt(Tau_wall/rho)

This is under log law equilibrium hypothethis, otherwise....

Hope that helps,

Sylvain