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Old   May 17, 2013, 17:26
Default Moving mesh problem
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Hello,

I have just gone through the OpenFOAM's movingCone tutorial. I can see that, as the object moves to the right side, mesh on the right side is contracting and the mesh on the left side of the object is expanding. Please see the pictures attached (movingCone_initial.png and movingCone_last.png)

movingCone_initial.jpg

movingCone_last.jpg


After that, I tried to apply the same principles to a ship traveling through calm water making a 45 degree angle with the stream. I want to make the ship move 4 times the length of the ship, but my run crashes a little bit after the start. I think that is because the distortion of the mesh. Please see the pictures attached (ship_initial and ship_last)

ship_initial.jpg

ship_last.jpg


Do you know if there is a way to overcome that distortion problem? (Like updating and recreating the mesh in each step)

Thank you very much for your help in advance,

Kilroy
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Old   May 18, 2013, 03:22
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Basically you try to use a 2D example and run it in 3D... Well, it is always a mess. Moreover, the example you took uses a structured mesh while you use an unstructured mesh. If I understand well, you want to use the layer add/remove solver ?

For displacement into an unstructured mesh, I usually use the Laplacian solver. But this kind of technique is not very good for large dispalcements.
dynamicMeshDict file:
Code:
dynamicFvMesh      dynamicMotionSolverFvMesh;

motionSolverLibs ("libfvMotionSolvers.so");

solver            displacementLaplacian;

displacementLaplacianCoeffs
{
    diffusivity       quadratic inverseDistance (wall);
}
What you can try is to create 3 different areas. Two structured on each side of your domain and in the middle you put your boat. You then have to translate all your middle area (with the boat) so that the 2 areas on the side take the motion by adding/removing layers.
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Old   May 20, 2013, 16:36
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Frederic,

Thank you very much for your response. Dividing the computational domain into three parts is a very good idea, but I have no experience with that.

Do you know any example or tutorial for OpenFOAM, that applies the principles that you have described above?

Sincerely,

Kilroy
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