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June 13, 2013, 16:18 |
FSI analysis for blood vessel
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#1 |
New Member
Join Date: Jun 2013
Location: California
Posts: 12
Rep Power: 13 |
Since it says turn on element shape checking, in mechanics shape checking is on standard mechanical. By the way it says to change if error message occurs after first step. The error occurs after 6th iteration.
Hi everybody I am trying to simulate an aneurysm in a vessel. At the very beginning of simulations I encountered with problems. In the threads I have seen similar problems but can not get a solution, unless I missed it. First of all when performing on the CFX Setup it warned as: In Analysis 'Flow Analysis 1' - Output Control: No intermediate transient results files have been defined. In Analysis 'Flow Analysis 1': Export results are unavailable as no suitable boundaries exist for use as export surfaces. Mesh motion on a boundary invalidates its use as an export surface. I ignored those. Then in the out file when solving structural before cfx: A wall has been placed at portion(s) of an OUTLET | | boundary condition (at 95.7% of the faces, 96.6% of the area) | | to prevent fluid from flowing into the domain. | | The boundary condition name is: Outlet. | | The fluid name is: Fluid 1. | | If this situation persists, consider switching | | to an Opening type boundary condition instead. And then: Fatal error occurred when requesting Total Mesh Displacement for Interface. In the error file it says: *** ERROR *** CP = 62.931 TIME= 12:34:42 One or more elements have become highly distorted. Excessive distortion of elements is usually a symptom indicating the need for corrective action elsewhere. Try ramping the load up instead of step applying the load (KBC,1). You may need to improve your mesh to obtain elements with better aspect ratios. Also consider the behavior of materials, contact pairs, and/or constraint equations. If this message appears in the first iteration of first substep, be sure to run shape checking of elements. I am attaching the out and error file. When I increase the mesh quality nothing changed. Only I get the error after waiting a little longer ) I will really really appreciate if someone can answer. PS: I also attach the fluid & solid mesh with the weird picture in the results ( in case it may give some idea what is wrong) Last edited by faraday34; June 13, 2013 at 19:03. Reason: I get no answer |
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June 18, 2013, 17:08 |
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#2 |
New Member
Join Date: Jun 2013
Location: California
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For the ones who also questions such kind of question
Increasing young modulus of elasticity of the wall, making it in GPa made the solution converge. |
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June 19, 2013, 03:25 |
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#3 |
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Lance
Join Date: Mar 2009
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June 19, 2013, 11:54 |
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#4 |
New Member
Join Date: Jun 2013
Location: California
Posts: 12
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It is not realistic, but since I am at the beginning I was even not using blood, just water and trying to see if the model works. Geometry, mesh, fsi interface etc. Bcs are also need to be modified.
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June 19, 2013, 19:09 |
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#5 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,826
Rep Power: 144 |
I think Lance's comment is important - if the stiffness you use is a long way from the real stiffness then the setup is not going to be relevant for the real simulation. Change the stiffness to be at close to the actual stiffness.
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