I'm trying to simulate the behaviour of a thin, malleable plastic structure. This plastic bag-like body is located underwater. It has a weighter mass in the base to hold it down, a volume of water through the mid section, and a volume of air in the upper section which holds the material up. Unfortunately I cannot provide images due to IP considerations.
At this point I havent added the air or weights. I'm just trying to fix the bottom of the structure and apply hydrostatic pressure to the inside and the outside of the body. I'm using brick elements for the moment, but may switch to plate or membrane elements. I'm modelling 1/4 of the body since it is symmetric. The simulations converge and the results look resonable. When I add gravity however, my displacements decrease by a factor of three. This phenomenon is odd because gravity acts in a direction that ought to increase the displacements.