about wall shear stress
 

the flow of liquid on structured wall is treated. from the plot of velocity vector, the eddy near the wall appeared. but i want to verify it from the wall shear stress. the plot of wall shear stress v.s. wall is made. but all the stress is positive. i think some of these should be negative. why?
and how can i get the velocity gradient normal to the wall?

anyone can offered some suggestions？

Only the magnitude of the wall shear stress shown here, directional information can be obtained from the components of the wall shear stress included as well. Good lcuk

thanks for your reply. how to calculate the wall shear stress in fluent? is this the magnitude of this vector?

Wall shear stress can be found under Wall fluxes or something, good luck.

i know the position of wall shear stress. but do not know how to calculate it in fluent. please give some explanations.