Learning Forum

[fares abbara]

Hello,

I have been working on an FSI model of fluid flow in a deforming tube. The tube is modeled as a surface body and a thickness of 1mm is given to it. the tube is fixed at the inlet and outlet edges. for the fluid domain i have set the boundary conditions as inlet velocity and outlet pressure. outlet pressure is set at 1333 Pa and the inlet velocity is time dependent such that it is a sign wave with period of 0.5s. I am running my simulation for 0.6 seconds and started with time step of 0.01s. The simulation runs fine with the following time step. however i would like to reduce the time step to 0.002 and 0.001s.  the problem is that with 0.001s i get excessive deformation error. the figure attched shows the deformation being exhibited at the first 2 steps. My question is what could possibly be the relationship between time step size and such excessive deformation ?

[Federico Alzamora Previtali]

Hello, 

hard to say from this figure alone, but I would suggest saving intermediate .dat files to check how your solution is evolving. Examining those intermediate steps would give you a better idea of what is happening.