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-   -   Change parameter and run cases parallel (http://www.cfd-online.com/Forums/ansys/91075-change-parameter-run-cases-parallel.html)

lingdeer July 29, 2011 10:27

Change parameter and run cases parallel
 
Hi,

I am running 2 way FSI on blood vessel using ANSYS workbench and CFX. It's a cylinder, 20mm diameter, 200mm length, 3mm thickness.
I have a lot of issues even start to run the simulations, and always get this error: "Fatal error occurred when requesting Total Mesh Displacement for Interface"

Only one case that works so far, I impose a pressure pulse of 0.01s (peak 1600 Pa) and 0.01-0.02s 0 Pa, I used both Hex meshes for solid and fluid.
Time step = 0.001s, Step end time = 0.02s. And this is the only case that works (Young's modulus = 1.33e7). Outlet boundary is opening type, pressure =0.

Since I m trying to make it more physiologic, I need to lower down Young's modulus to 1.33e5 - 1.33e6. But once I change that the error that I mentioned show up.

Also, I am trying to impose velocity/flow boundary conditions because that's something I need to do eventually. However, I tried different times and same error stopped my simulations again at the first time step. I read some forum threads but I didnt get the exact solution of my problem. So I have a couple of questions hope anyone can help me with:

1) Since I want to play with different parameters: e.g. mesh type, mesh size, time step, inlet outlet profiles on the same ansys workbench file to fine tune to the condition I need, I don't want to setup cases for each of them. Instead, I want to run them all at the same time as I can run on different nodes on my server. I wonder is there anyway to do that, instead of creating many different workbench file to do that?

2) How can I determine the best time step of my problem? (I guess if I can figure out the 1st problem then I can try running with different timesteps here)

3) I wonder do I need to add some sort of stability/source term at my FSI boundary? I am a newbie to FSI simulations so if anyone can offer me some guidance it would be greatly appreciated.

Thanks a tonne in advance! :)


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