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Axis of Rotation changed in CFD

756 Views, 10 Replies
08/07/2013 12:42 PM

Hello,

I'm trying to make a transient simulation of a centrifugal pump. But I have a problem with the axis of rotation of the rotating frame. I have verified that the axis of rotation with the body of the pump housing is the same. But when I'm starting the simulation, the rotating part makes an elliptical movement around the original axis.

 

I have checked the CAD model several times, how can I avoid this problem?

 

 

ATTACHMENTS:
rr.jpg

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Message 1 of 10 ( Views: 756 )

Re: Axis of Rotation changed in CFD

08/13/2013 11:45 AM

We tried to simulate only the impeller (single channel impeller) in a cylindrical volume. The same problem occurred. So it isn't possible in Simulation CFD 2014 to solve highly unbalanced impellers?

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Message 2 of 10 ( Views: 726 )

Re: Axis of Rotation changed in CFD

08/15/2013 7:50 PM

As I understand, your rotating impeller doesn't have the center of mass inline with the rotational axis which is what you mean by unbalanced rotating device?



Royce.Abel
Technical Support Manager


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Message 3 of 10 ( Views: 687 )

Re: Axis of Rotation changed in CFD

08/16/2013 9:31 AM

Yes, exactly. I supposed that the moment of inertia is not taken into account when simulating a rotating region. But the position of the center of mass influences the simulation?


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Message 4 of 10 ( Views: 666 )

Re: Axis of Rotation changed in CFD

08/16/2013 1:39 PM
Can you post the ##_support.cfz file or PM it to me?

If it is too large use dropbox or A360 to upload the file and provide a link for me to download.

Thanks!


Royce.Abel
Technical Support Manager


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Message 5 of 10 ( Views: 662 )

Re: Axis of Rotation changed in CFD

09/03/2013 3:06 PM
have you got any news here? have seen this now also for a few models...

Dipl.-Ing. (FH) Marco Müller
Application Engineer Digital Simulation
Mensch und Maschine Deutschland GmbH
www.mum.de/cfd


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Message 6 of 10 ( Views: 619 )

Re: Axis of Rotation changed in CFD

09/04/2013 8:03 PM

The rotating region material is designed to work with geometry that is periodic in nature and doens't work well for instance when you have a 1 bladed fan.  There are various reasons for it, but those reasons aren't all that important.  

 

The most appropriate workaround would be using the full motion package.

 

Another option which I think might work for Solidworks users (not sure if you can do this in other CAD packages) is that you can override the material properties and define your own center of mass.  I seem to recal a few years ago a user that had this specific problem and was able to get it to rotate around the center again after making these adjustments.  Maybe something to consider?  Otherwise you will have to use the motion solver.

 

-Royce



Royce.Abel
Technical Support Manager


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Message 7 of 10 ( Views: 611 )

Re: Axis of Rotation changed in CFD

09/05/2013 6:47 AM

It has been confirmed that single-channel impellers can not be simulated with rotating region, if the center of mass is not inline with the rotaional axis. But we have solved the problem by eliminating the imbalance of the impeller (in places that are not integrated into the simulation). Now the rotation axis no longer shifts.

But this solution is only possible, if not the entire impeller is involved in the simulation.


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Message 8 of 10 ( Views: 605 )

Re: Axis of Rotation changed in CFD

09/05/2013 11:18 PM

So you added a counter balance that was built into your rotating solid?

 

-Royce



Royce.Abel
Technical Support Manager


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Message 9 of 10 ( Views: 599 )

Re: Axis of Rotation changed in CFD

07/17/2014 8:05 AM

We added a cavity to the cover plate of the impeller, and closed it except a small gap (when its fully closed, the center of mass is still not inline with the axis of rotation).

This solution works best.

 

ATTACHMENTS:
Impeller.jpg

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Message 10 of 10 ( Views: 336 )