[Beingzzz]

hi everyone.

I am very confused about the wall shear stress output in openfoam, and I have always believed that his calculation formula is as follows
https://www.cfd-online.com/Wiki/Wall_shear_stress

However, I used the post-processing tool"postProcess -func wallshaearstress/grad(U) " to output the velocity gradient and shear stress of the wall, and it can be seen that they do not correspond at all. Therefore, I would like to know the output format of the velocity gradient in openfoam are dxU dxV dxW dyU dyV dyW dzU dzV dzW or dxU dyU dzU dxV dyV dzV dxW dyW dzW.
And The calculation method of wall shear stress, I understand that there must be relevant formulas in the code, but please forgive me as a beginner, I have not found the relevant part, can anyone help? Thank you very much.
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