# Fluid Structure Interaction with FEniCS

**URL:** <https://fenicsproject.discourse.group/t/fluid-structure-interaction-with-fenics/7384>\
**Category:** Uncategorized\
**Created:** [December 28, 2021, 9:13am UTC](https://fenicsproject.discourse.group/t/fluid-structure-interaction-with-fenics/7384 "2021-12-28T09:13:25Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Alberto\_Lolli](https://avatars.discourse-cdn.com/v4/letter/a/b19c9b/32.png) [@Alberto\_Lolli](https://fenicsproject.discourse.group/u/Alberto_Lolli)\
**Post date:** [December 28, 2021, 9:13am UTC](https://fenicsproject.discourse.group/t/fluid-structure-interaction-with-fenics/7384/1 "2021-12-28T09:13:26Z")

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Hello everyone, has someone any ideas on how to impose a rotational velocity on a body immersed in a channel? The situation is the following: I want to compute the flow pass through the body and make the body moving by a rotation of itself. I’ve implemented the fluid simulation, and I’ve meshed the boundaries of the body, now how can I set this velocity condition on the body? The attached image represent the pressure field, just to show the geometry.

 ![pressure](https://global.discourse-cdn.com/free1/uploads/fenicsproject1/original/2X/5/5cbefe5f494c8a89e96161c616ea3bd165ec2e70.png)  
Many thanks in advance

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**Author:** ![Massimiliano\_Leoni](https://yyz2.discourse-cdn.com/free1/user_avatar/fenicsproject.discourse.group/massimiliano_leoni/32/584_2.png) [@Massimiliano\_Leoni](https://fenicsproject.discourse.group/u/Massimiliano_Leoni)\
**Post date:** [January 3, 2022, 2:28pm UTC](https://fenicsproject.discourse.group/t/fluid-structure-interaction-with-fenics/7384/2 "2022-01-03T14:28:50Z")

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I am not sure this is supported at the moment. Given the symmetry of the domain, would it make any sense to switch to a reference frame on the rotating body and apply the rotation to the cylinder instead? Then you don’t need to move anything because the cylinder is axisymmetric.

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**Author:** ![nate](https://yyz2.discourse-cdn.com/free1/user_avatar/fenicsproject.discourse.group/nate/32/17_2.png) [@nate](https://fenicsproject.discourse.group/u/nate)\
**Post date:** [January 3, 2022, 3:32pm UTC](https://fenicsproject.discourse.group/t/fluid-structure-interaction-with-fenics/7384/3 "2022-01-03T15:32:43Z")

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Surely the body’s rotation can be imposed via an appropriate boundary condition relative to the reference frame of the volume?

Or perhaps I misunderstand the question, and the rotation is induced by the flow? In which case much more care must be taken. Perhaps see @kamensky’s [lecture notes](https://david-kamensky.eng.ucsd.edu/teaching/mae-207-fea-for-coupled-problems).

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**Author:** ![Alberto\_Lolli](https://avatars.discourse-cdn.com/v4/letter/a/b19c9b/32.png) [@Alberto\_Lolli](https://fenicsproject.discourse.group/u/Alberto_Lolli)\
**Post date:** [January 4, 2022, 10:10am UTC](https://fenicsproject.discourse.group/t/fluid-structure-interaction-with-fenics/7384/4 "2022-01-04T10:10:51Z")

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Well, I’ve think about that, the problem is that later the geometry will be more complex (adjoint of 4 helices) and not all parts are rotating at the same speed, then this solution cannot be applied.

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**Author:** ![Alberto\_Lolli](https://avatars.discourse-cdn.com/v4/letter/a/b19c9b/32.png) [@Alberto\_Lolli](https://fenicsproject.discourse.group/u/Alberto_Lolli)\
**Post date:** [January 4, 2022, 10:11am UTC](https://fenicsproject.discourse.group/t/fluid-structure-interaction-with-fenics/7384/5 "2022-01-04T10:11:42Z")

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How can I set a rotating boundary condition in the fluid around the body ? which equation should I write?