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Constraints problem in FSI

Posted 16 giu 2021, 11:28 GMT-4 Computational Fluid Dynamics (CFD) Version 5.1 1 Reply

Muslim Safi
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hello! i am trying to simulate a fluid-structure interaction model, and when i click solve its giving me an error "Constraints found for variables in different segregated groups. try to merge these groups" what does that mean and how do i merge those groups?

1 Reply Last Post 26 giu 2021, 20:49 GMT-4
Nagi Elabbasi Facebook Reality Labs
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Posted: 3 years ago 26 giu 2021, 20:49 GMT-4

This error means that you are using a Segregated Solver, which in many FSI problems is the default solver. The structural degrees of freedom are most likely in one segregated group, the fluid degrees of freedom in another, and the fluid mesh displacements in a third one. However, you have some constraints that involves two of these three types of degrees of freedom in a single equation. The easiest way round this problem in my opinion is not to merge these groups but to use a Fully Coupled Solver instead of a segregated one. Be careful though that the fully coupled solver requires more memory.

I hope this helps. Nagi Elabbasi

This error means that you are using a Segregated Solver, which in many FSI problems is the default solver. The structural degrees of freedom are most likely in one segregated group, the fluid degrees of freedom in another, and the fluid mesh displacements in a third one. However, you have some constraints that involves two of these three types of degrees of freedom in a single equation. The easiest way round this problem in my opinion is not to merge these groups but to use a Fully Coupled Solver instead of a segregated one. Be careful though that the fully coupled solver requires more memory. I hope this helps. Nagi Elabbasi

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