Discussion Forum

I’m using form assembly in a model because I want one domain to slide across another. On the bottom of the upper domain, I have prescribed displacement in the y direction but not in the x or z direction. However I also have gravity acting on both domains. This causes the upper domain to fall all the way through the bottom one. How can I prevent this from happening?

Prescribing a z displacement of 0 on the boundary keeps this from happening, but then the boundary of the upper domain isn't free to deform around bumps in the lower one as it slides in the y direction. I’ve tried setting up an identity boundary pair between them, which prevents this problem, but I don’t want to use a pair boundary condition because I don’t want to have a prescribed velocity on the boundary of both domains, just the upper one. I’ve also tried having one side boundary of the upper domain be fixed, which seems to prevent this problem, but that’s not actually the boundary condition I want to have there.