I have an OpenFOAM simulation wich gives me the p, Ux, Uy, Uz and T coutures. I want to calculate the total drag including the hydrostatic and viscous elements, on some surfaces. I have followed this tutorial and I’m able to calculate the hydrostatic part. however all of the examples I see on the internet ignore the vicious part. Although in the end it can be shown that it is negligible but I have to show it in my study.

There is a filter called Gradient Of Unstructured DataSet and if I apply it on U:

It generates 9 elements as expected:

The first issue is that I don’t know which element refers to ∂Uz/ ∂x which in my case should be the vicious stress. It must be 2 or 6 but not sure.

the second issue is when I want to apply the calculator filter to calculate 𝜂∂Uz/ ∂x in Attribute section>cell data there are not gradients, but they are in the point Data:

I would appreciate if you could help me solve this issue. maybe if there are any examples for calculating viscous stresses on an object that could give me some clue. Thank sin advance.