Calculation of shear stress components
How is the 'wall shear stress' evaluated from the individual shear stress components (Xwall, Ywall, Zwall)? 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 postprocessed. For a 2D case there will be X and Y component. Wall shear stress = SQRT(Xwall^2 + Ywall^2) In order to confirm this a Custom field function (CFF) could be created and then verfied that the values of the cff and wallshear stress are identical. 

