FSI in a closed system

Dear all

We are having some erratic results when trying to model the variation in pressure and flow (using FSI) in a fluid which is fully encapsulated in a polymer membrane. The idea is that by applying a pressure on the polymer we cause the fluid to move and apply a pressure elsewhere (as determined by the architectue of the polymer case).

First of all we set up the problem by defining:

1) The pressure applied to the polymer
2) The initial pressure (an arbitary value) and the intial flow = 0

This did not seem to solve, following which we were advised to set a point in the fluid with a known pressure (constant throughout the simulation) This solved but does not really represent the true physics.

Is anybody able to advise on how best to set this problem up ? (usually in the FSI tutorials, the systems modelled are open flow with a known output and input flow, however it appears to be more complicated when setting up a closed system in which the fluid pressure and flow are dependent on the boundary conditions applied to the solid (polymer membrane)

Any help direction or advice would be very much appreciated.


Regards, Duncan