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LenDawg0220 July 28, 2012 12:54

UDF to control motion NOT about CG
 
Hello all, I'm in need of some guidance with regards to constructing a UDF for fluent, which restricts the motion of a 2D body.

The project I'm working on involves an object floating on the free surface of a multiphase system (exactly like the falling box example). I've currently written a UDF specifying the 6DOF properties and this works fine. My problem lies in how to restrict the motion of the object. When using the 6DOF solver, if I limit translation of the object in the x-direction, it does this about the objects CG. I would like my object to be, for the lack of a better term, "pinned" at a seperate location.

Another way to describe this would be to reference the falling box example again. For those that aren't familiar, in the example a box is dropped from a specified height into a 2D tank of water. In that example there are no restrictions on the motion of the box. Say I wanted to repeat that simulation but put the upper left corner of the box in a "slot". This would allow the box to travel in the y-dir, but would be restricted from moving in the x-dir, and the box would have to rotate about the upper left corner. This is all done whilst keeping the CG at it's proper location.

Thanks in advance for the guidance, it's much appreciated. If the above isn't clear enough, I can be more specific to what I'm working on.

Len


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