I would like to know the factors involved in the calculation of the wall shear stress
 

Hello, I am a student studying fluid dynamics simulation.

I tried to calculate the wall shear stress with several simulation programs, but there were parts where the overall wall shear stress was similar but the detailed smoothing degree was different depending on the simulation program.

Therefore, we are trying to make assumptions that there is a condition for the vector used when calculating the wall shear stress of one node on the wall, or that a separate smoothing process is performed after the calculation.

Is there any part of the document where I can find these parts? Thanks for your help.