Hi,
I am currently doing my PhD studies and I have a problem understanding the weak constraint/weak contribution in the Weak Form PDE toolbox. I'm trying to implement an RVE (Representative Volume Element) in 2D using Weak Form PDE. Everything worked great until I tried to implement a constraint equation.
The equation I need to implement as a constraint is in the following form:
vint(u*x) = 1
That is, I want to constraint the volume integral (in the whole domain) of u*x (where u is the displacement field in x-direction and x is just the nodal x-coordinates) to a constant value, here 1. I've tried using the Weak constraint node, but get singular matrix. The pointwise constraint works better, but the results are completely wrong (and give a great error).
Is there a way to implement such a constraint in Comsol, and how?
Thanks for any help!