Hi SfePy community,

I am attempting model stress and strain rate variations over a region (Omega) that contains sub-regions (Omega1 and Omega2) with different viscosities.

I have a general understanding of this mathematically, but i am still unsure the exact equations used by SfePy to calculate this. So far my model is largely based on the Navies-Stokes example provided in SfePy with the circle_in_square mesh (example here: https://pastebin.com/VZrEKVFZ). Ultimately I would like to be able to model linear and power law viscous flow, is this possible with the existing equations in SfePy?

More specific questions:

What are default units for pressure (p) the values range from ~ -50 to 50? How can I change or specify units if i need to?

How do you calculate strain rate? Can I use the GradTerm class to do this?: sr = problem.evaluate('ev_grad.i.Omega(u)', mode='el_avg')

When I try to calculate Cauchy stress i get error:

ValueError: wrong arguments shapes for "+1.00e+00 * ev_cauchy_stress.4.Omega(fluid.viscosity, u)" term!

I think this is because ev_cauchy_stress requires a 3x3 matrix material and I have input a single viscosity value? What is the best way to solve this?

Thank you!