Calculation of shear stress components
How is the 'wall shear stress' evaluated from the individual shear stress components (X-wall, Y-wall, Z-wall)?
Following is the expression for computing viscous shear stress components:
Tij = mu * ( dUi / dXj + dUj/dXi) - 2/3*mu*( div U) * (delta)ij
where (delta)ij = 1 for i = j, 0 for i != j
mu is the viscoisty of fluid.
Now this will give value of each component.
The magnitude of these components will give the wall shear stress which can be post-processed.
For a 2D case there will be X and Y component.
Wall shear stress = SQRT(X-wall^2 + Y-wall^2)
In order to confirm this a Custom field function (CFF) could be created and then verfied that the values of the cff and wall-shear stress are identical.