I am new to COMSOL and I want to model fluid flow in stress field. As starting point I want a simple 2D box having a fracture from right to left while pressure gradient vertically. I want to know the threshold value of that pressure from top which allows flow of fluid in fracture. Can anyone please suggest me which modules of COMSOL should I be using. I see simple fluid flow in fracture examples but not where impact of pressure controls the flow!