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-   -   Mesh Motion pitch on a hull (http://www.cfd-online.com/Forums/cfx/27045-mesh-motion-pitch-hull.html)

 Seb February 19, 2009 11:10

Mesh Motion pitch on a hull

I am trying to simulate a transient wigley hull in waves free to heave and pitch using CFX. My main trouble is how to specify the pitch of the hull (or the rotation of the mesh on the hull) in terms of CEL expressions, where the mesh motion can be only defined in Cartesian coordinates and it has to be independent of the heave, to give the right pitch at any time. For the conservation of angular momentum there is a velocity variation of the angle that has to be found, but it seems that CFX doesn't allow defining mesh motion in cylindrical components and the decomposition of the angle could be affected by heave, so in the end the pitch is not the real one.

Any ideas of how to specify the pitch of the hull (mesh on the hull) in terms of CEL?

 Edmund Singer February 23, 2009 14:04

Re: Mesh Motion pitch on a hull

Seb:

Here is a sample of motion I have used for a specific application. The item moves around the Y axis located at XL,YL,ZL. You need to supply the logic for alpha, which is the angular rotation

NewX=-((z-ZL)-Total Mesh Displacement Z)*sin(alpha)+((x-XL)-Total Mesh Displacement X)*cos(w*t)+XL

NewY=-((y-YL)-Total Mesh Displacement Y) +YL

NewZ=-((z-ZL)-Total Mesh Displacement Z)*cos(alpha)+((X-XL)-Total Mesh Displacement X)*sin(alpha)+ZL

You then use Specifed Location for the mesh motions using NewX, NewY, NewZ

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