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'Contact Detection' option disables Structure (FSI) in Fluent. negative cells volumes

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Old   August 11, 2020, 02:02
Question 'Contact Detection' option disables Structure (FSI) in Fluent. negative cells volumes
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Hi everyone.

I am using ANSYS FLUENT 2020R1 and working on flapper valve simulation with 2-way FSI enabled in Fluent. Structure is set as Linear-Elastic.

While running simulation, the flapper valve is supposed to block flow by coming in contact with the wall as soon as it comes near the wall, it gives error of 'Update-Dynamic-Mesh failed. Negative cell volume detected'.
To avoid this, I can think of 2 approaches.
  1. Use contact detection. The issue is that when I enable 'contact detection' option in Dynamic meshing, the Structure mode in Fluent gets disabled as shown in pics below. Is there any work around to get this enabled using UDFs.
  2. Vary Porosity of cells near the wall. I can create prism cells with a certain thickness near the boundary of wall and flap set their porosity to 0 so the flow get blocked before flap and wall get in contact. There are 2 issues with this approach.
a. For some reason, even after setting porosity to 0, flow is not completely blocked. what shall I do to make it block the flow 100%?

b. even if the flow gets blocked, the flap would keep on traveling towards the wall and end up with giving 'negative cell volume' error.

Can anyone please give guidance on how can this issue be solved?

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contact detection, fsi 2-way coupling, negative cell volume, porosity model

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