Two way FSI of a deformable pipe
I am new to FSI and have been working on a problem that involves a deformable pipe. The length of the pipe is 20 mm and the internal diameter is 3 mm. The thickness of the pipe is 1 mm. I am trying to simulate flow of water in the pipe for the case when the rear portion of the pipe (last 5 mm ) is made up of a more compliant material and has a pulsating external pressure being applied to it. Water flows into the pipe at 0.5 m/s for which I have used a velocity-inlet condition. What i am hoping to achieve is that due to deformation of the pipe at the rear end, there is reversal of water flow and it flows back towards the inlet. When I run the system coupling, it throws an error which says 'negative volume detected.' I have tried decreasing the time step and that has not helped. For a different run, I got an error which said that excessive distortion of some elements in the transient structural module is detected. I have tried refining the mesh and ramped the load over a much larger time. Could someone please help me troubleshoot the problem? I have attached the workbench file below.