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felicemastronzo May 3, 2012 06:08

HELP !!! Please !!! Periodic BC
Hi all,
I try to obtain the same results like in the following pdf (see fig 7)

I have create the geometry (like fig 7 in the pdf but only with one gap between two teeth) made by 1 single volume, 1 wall (the profile of the gear, 2 periodic bc on the sides , 1 symmetry plane (like in the pdf I have modeled only the half of the gear) and two p-outlet (one is planar ant the other has a curvature radius) ). I want to perform a steady simulation. In order to describe the rotation of the gear, I have imposed only a rotation to the walls (corresponding to the teeth profile). Is it correct? The results I get are strange and I want to know if I have made some settings mistake. Should I impose also a rotation to the volume? Should I change some periodic setting?
All kind of help is welcome!


felicemastronzo May 3, 2012 09:23

Nobody can help me?


delaneyluke May 7, 2012 02:28

A moving (rotating) wall alone won't help, you need to define a rotating reference frame as well. Use the option of "frame motion" with Fluent.

P.S. The paper specifies that the equations are solved in a rotating reference frame.


felicemastronzo May 7, 2012 05:55

so I have just to apply a rotating ref. frame or also some moving B.C.?


delaneyluke May 7, 2012 06:12



felicemastronzo May 7, 2012 07:20

Thanks a lot!
If I have correctly understand I have to impose a rotation to the ref. frame and the same rotation to the gear boundaries (walls). The periodic boundaries, the symmetric boundary and the p-out boundaries, instead, are steady... correct?
But if the ref. rotates, the gear boundaries (that are moving) becomes steady (in the rotating ref.) and the other ones becomes moving boundaries. So in order to have the right results, I have, for example, to plot all the relative velocities instead the absolute ones, right?


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