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idrama July 7, 2011 02:58

Hello Foamers,

I have a simple question about computing wall shear stresses: what is the difference between:

(1) tau_w=mu*grad(U) | y=0


(1) tau_W=mu [ grad(U)-grad(U)^T ] . n

where mu is the viscosity, U the velocity and n the surface normal.


David* July 11, 2011 05:37

Hi Claus,
the second one makes no sense to me, why would you substract a transposed tensor from it's original? Where did you find this formula?

idrama July 11, 2011 09:37

It can be found in several books about mechanics; there it is treated as the generalization of newtons law. The term even appears in the incompressible navier stokes equation.

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