Thank you for the response. Unfortunately, it didn’t resolve my issue. I am working on shortening my code and will send it here again. In the meantime, I came across this post. it seems that I should not use mixed element. I also read the post here and it seems it is not recommended using a mixed element instead of the block formulation.
Is it advisable to use mixed elements in a block formulation?
I read the Test problem 2: Flow past a cylinder, I also read the The Stokes equations and mixed element was not used in this examples. Is there a reason for that?
Do you think the way I have organized my code is appropriate? Specifically, I’m referring to using mixed elements, creating the variational form in a blocked discrete system, and then assembling the nested system.
Thanks