[Taral Patel]

Hello Everyone, Thank you for taking your time to go through my post for extending your help!!

I am working to simulate the dynamic response of an aorta for time varying mass flow rate. I am setting up a Fluid Structure Interaction(FSI) problem using StarCCM+ (Fluid) and Abaqus (Strutural) software. These are the list of errors I am facing. I am following the Plate FSI tutorial that is in the StarCCM+.

1. After setting up the simulation in StarCCM+ and specifying material properties in Abaqus my simulation only runs for two time steps in StarCCM+ and then it gives me non positive mesh error. When I take a look at geometry it is deformed way too much and it literally expand beyond physcially possible.

2. If I change the material properties in Abaqus from young's modulus of heart to 10x or 20x or 100x times youngs modulus of heart then it gives me same error but after 10 - 11 time steps.

3. Initially I was using 0.005s of time step but then I thought it might give too much pressure gradient. So I reduced the time step to 1e-6 seconds which still gave me the same error.

4. Co-simulation displacement residual always stays at zero and then simulation crashes with non positive cell volume.

To make things easier I decided to setup an FSI simulation for a straight hollow pipe with 4mm thickness and material properties of heart and flow rate of heart. For aorta/heart I used tetrahedral mesh and for pipe I used trimmed mesh cell.

In case of pipe with one inlet and one outlet, I am facing the same issues as mentioned above.

I am using Morhing tool to simulate the dynamic displacement of wall. Inlet and outlet are specified Floating morpher specification and FSI interface wall is specified total displacement morpher specifiction.

Geometry information of aorta. Inlet (1), main outlet(1), secondary outlets(4), ~2 - 3 mm thick wall, complex geometry,
Morpher specification - Inlets and outlet (Floating morpher)
Wall (Total displacement morpher)


I am solving these errors for 4 months now and I am open to any suggestions. If any more details are needed please let me know.