# Problems with circular shapes in FSI simulations

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 September 15, 2009, 09:01 Problems with circular shapes in FSI simulations #1 New Member   ronald Join Date: Sep 2009 Posts: 10 Rep Power: 9 Sponsored Links Hello, I am working on a impact model of the human head. Skull, Cerebrospinal fluid (CSF) and the human brain. First I made a very simple model without the brain. Just a simple square filled with the CSF. There is a force applied (starts at 3e-5 seconds ends at 9e-5 seconds ) at the front of the square which represents the impact. BUT when I model the brain in this square (see it as a circle in a square, around the square is the CSF) the simulation stops always at the timestep when the force will come up. I tried all different kind of meshes and it didn't help. Maybe the problem is the density of the brain and the fluid, because they are almost simular?? end time = 3e-3 time step = 3e-5 Hope someone can help me. Kezman

 September 15, 2009, 09:42 UPDATE: error text #2 New Member   ronald Join Date: Sep 2009 Posts: 10 Rep Power: 9 +--------------------------------------------------------------------+ | ERROR #001100279 has occurred in subroutine ErrAction. | | Message: | | CFX encountered the error: Read. Fatal error occurred when reque- | | sting Total Mesh Displacement for Boundary 1. | | | | | | | | | +--------------------------------------------------------------------+ +--------------------------------------------------------------------+ | ERROR #001100279 has occurred in subroutine ErrAction. | | Message: | | cplg_SendCommand failed to send the command: ERROR -- CFX encount- | | ered the error: Read. Fatal error occurred when requesting Total | | Mesh Displacement for Boundary 1. | | | | | | | +--------------------------------------------------------------------+ +--------------------------------------------------------------------+ | Writing crash recovery file | +--------------------------------------------------------------------+ +--------------------------------------------------------------------+ | ERROR #001100279 has occurred in subroutine ErrAction. | | Message: | | Stopped in routine cplg_SendCommand | | | | | | | | | | | +--------------------------------------------------------------------+ +--------------------------------------------------------------------+ | An error has occurred in cfx5solve: | | | | The ANSYS CFX solver exited with return code 1. No results file | | has been created. | +--------------------------------------------------------------------+ End of solution stage. +--------------------------------------------------------------------+ | The following transient and backup files written by the ANSYS CFX | | solver have been saved in the directory | | /scratch/ronald/square_withBrain/square_withBrain_CSF_003: | | | | 1_CS.trn, 0_CS.trn | +--------------------------------------------------------------------+ +--------------------------------------------------------------------+ | An error has occurred in cfx5solve: | | | | ANSYS Solver terminated with return code 256 | +--------------------------------------------------------------------+

 September 15, 2009, 18:24 #3 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,732 Rep Power: 106 Could it be that the CSF domain gets squeezed so thin the mesh goes to zero thickness (or inverts)? You should output the mesh at several time steps to get a feel for how the mesh is moving. You may also be able to do this using the immersed grid feature in V12.

 October 3, 2012, 16:07 #4 Member   Hesam Moghaddam Join Date: Mar 2012 Posts: 49 Rep Power: 7 I am modeling head with 3 parts: skull, CSF and Brain The two-way FSI example in ANSYS tutorial only mentions 1 solid parts and one Fluid part. When I define two interface between solid and fluid 1 for Skull-CSF and one for CSF- Brain I get error that the solver can not get the total mesh displacement for CSF-Brain interface. Do you have any idea what the problem can be? Thanks

 Tags circular shape, close density, fsi

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