# A quick question about sixDofRigidBodyMotion

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 January 23, 2022, 17:05 A quick question about sixDofRigidBodyMotion #1 Member   WY Join Date: Mar 2020 Posts: 36 Rep Power: 6 Hi, I use sixDofRigidBodyMotion to solve a 2D FSI problem (vortex induced vibration of cylinder). But I am a little confused about the functionality of this solver. In the problem involving dynamic mesh, we need to solve mesh motion equation, and the common solvers include displacementLaplacian, velocityLaplacian, etc. And a template is shown below: Code: ```dynamicFvMesh dynamicMotionSolverFvMesh; motionSolverLibs ("libfvMotionSolvers.so)"; solver displacementLaplacian; displacementLaplacianCoeffs { diffusivity quadratic inverseDistance 5.0 (Body1 Body2); }``` Take displacementLaplacian as example, it solves mesh motion by laplacian equation of diffusivity and mesh displacment. In the FSI problem, we need to solve both mesh motion and body motion. And it seems that sixDofRigidBodyMotion can solve motions of mesh and body, just including all the settings (mesh morphing definition, body definition, etc.) in dynamicMeshDict file. The template is shown below: Code: ```dynamicFvMesh dynamicMotionSolverFvMesh; motionSolverLibs ( "libsixDoFRigidBodyMotionDev.so" ); solver sixDoFRigidBodyMotion; sixDoFRigidBodyMotionCoeffs { //parameters }``` If I understand correctly, we first solve body motion (displacement, velocity, acceleration) from this solver, and the mesh deformation region is defined by outerDistance and innerDistance. But how to determine the motion of internal mesh grids within these two distances, just by default diffusivity model (inverseDistance linear)? Sorry about the disordered description. I just don't know what exactly sixDoFRigidBodyMotion solver done in OpenFOAM. I am very appreciated for any suggestion!

 December 23, 2022, 02:25 Same Problem #2 New Member   MoHammmmed Join Date: Sep 2012 Posts: 1 Rep Power: 0 Sorry I have the same problem, did you figure any solution ??!

 October 18, 2023, 10:17 #3 Member   Martin Join Date: Dec 2011 Posts: 40 Rep Power: 14 Hi, have you solved this problem? We are having the same issue controlling the mesh motion when solving FSI problems.

October 19, 2023, 02:39
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WY
Join Date: Mar 2020
Posts: 36
Rep Power: 6
Quote:
 Originally Posted by msaravia Hi, have you solved this problem? We are having the same issue controlling the mesh motion when solving FSI problems.
Hi,

Sorry I am afraid I cannot give your much more details about the mesh motion. The focus of my case is the motion of body. I try different mesh motion solvers, and it has little influence on the results. So finally I just use the default mesh deformation method in OpenFOAM. There isn't much information on the Internet about how the mesh moves in OpenFOAM. So if you want to know more details or define your own mesh motion solver, maybe you can look into the source code.

 Tags dynamic mesh, sixdofrigidbodymotion

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