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Different solutions for Rotating Reference Frame

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Old   July 18, 2012, 13:12
Angry Different solutions for Rotating Reference Frame
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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.
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File Type: jpg 2Dgeometryrotatingshaftonly.jpg (48.3 KB, 14 views)
File Type: jpg 2Dgeometryrotatingframeshaft.jpg (47.3 KB, 10 views)
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Old   July 24, 2012, 10:06
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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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