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-   -   Different solutions for Rotating Reference Frame (http://www.cfd-online.com/Forums/fluent/104919-different-solutions-rotating-reference-frame.html)

fafou09 July 18, 2012 13:12

Different solutions for Rotating Reference Frame
 
2 Attachment(s)
Hi,
I am sort of a beginner in Fluent and ICEM, but I am using those software to model flows in a reactor.
The main model is a 3D one, but due to strange results I am now using only a 2D model to understand where the problems are coming from (basically a cylinder with a shaft).
The problem I have comes from the velocity observed near the outer wall of the cylinder.
I observe 2 cases:
1) rotating reference frame with velocity of 100 rpm, rotating shaft with 0 relative velocity and rotating walls with 0 absolute velocity
2) stationary frame and walls with rotating shaft at 100 rpm.

In the case 2, I have a good behaviour: the velocity decreases until 0 at the wall. However, in the case 1, it decreases then increases near the walls and is 0 at the wall.
But this increase does not make sense and the results should be the same in both case.

Am I missing something with the rotating reference frame, because in this case it is ok to use a stationary frame but for the 3D model with impeller, I will very likely need to use the rotating one.

I attach the velocities in both cases so that you may understand better my problem.

Thank you for your help.

fafou09 July 24, 2012 10:06

Does anyone have already seen the same problem?
It does not make sense to me, but I really do not understand why I have this difference in the solution.

Thank you very much!


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