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geri October 12, 2007 17:42

dynamic mesh bondary layer cells
Dear experts,

I am trying to analize the rigid body moving capabilities in fluent in case of bridge deck section flutter assassement. I applie a boundary layer mesh and I want this region move with the rigid body and not to deform or change. Can it be achieved???


Giles October 13, 2007 21:41

Re: dynamic mesh bondary layer cells
Make the spring constant in the DM smoothing settings 0, so the movement is spread as globally as possible. In addition if possible make the UDF move the deforming surface 10% of what you need it to move, then perform 10 mesh updates with it, so each step is small. This worked for me, hope it works for you.

geri October 14, 2007 07:26

Re: dynamic mesh bondary layer cells
Dear Giles!

Thanks for Your answer, the zero value of the spring factor solves the problem, the boundary cells move beautifully with the rigid body. I just don't understand what You mean the 10%!!! (My UDF is the simples as it can be, it defines a prescribed motion of a body).

Many thanks,


Amr October 16, 2007 07:16

Re: dynamic mesh bondary layer cells
Hi, If you have already a simple UDF (compiled ofcourse), then you can assign the UDF to both the body as well as the boundary layer. This would give the exact prescribed motion to the cernters of gravity of both.

To do so, you may want to have a look on the 6DOF UDF made on the fluent users website (need to have an access) and make use of the "calls" and "Num_Calls" variables. This is just for calling the function twice before writing the new locations on centers of gravity, thus enabling motion for both of your Blayer and the body itself.

If you find this difficult, you can still live with the low spring constant afterall.


Geri October 16, 2007 09:47

Re: dynamic mesh bondary layer cells
Dear Amr,

This solution seems to be the best, i will try it.

Many thanks

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