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-   -   MRF problem (http://www.cfd-online.com/Forums/fluent/50052-mrf-problem.html)

Amir December 15, 2008 09:59

MRF problem
 
Hi,

In my case there is one vertical axis wind turbine consist of 10 vertical blades which is rotating with constant speed.

I placed this turbine inside one cylinder with the same radius as turbine base. I sketched the second cylinder which contains the first one with the same shape but with bigger radius.

these two cylinders are specified as an interior. these two cylinders are specified as one fluid in Gambit and will be specified to rotate with constant speed in Fluent as a MRF.

After running simulation its demonstrated that the inner side cylinder is acting not like an interior.

I need help to understand what the problem is.

I appreciate your concentration.

Regards.

Magic December 16, 2008 08:57

Re: MRF problem
 
Amir,

How are the inner and outer cylinders connected? Did you subtract the inner form the outer? Are they connected? Please provide more detail of your geometry creation process?

Thanks

Khan

Amir December 17, 2008 15:44

Re: MRF problem
 
I subtract the turbine from the inner cylinder and I split the outer and inner cylinder to each other. They are connected to each other.

Thanks

Amir

Yasser Selima December 17, 2008 21:57

Re: MRF problem
 
I don't understand why did u use two cylinders. You can subtract the turbine from the outer cylinder and then you will have only one cylinder (interior) which should rotate on MRF.

Amir December 18, 2008 09:17

Re: MRF problem
 
Hi.

I was wonder if the cylinder radius which will turn by MRF is bigger the results are more accurate. I can generate mesh just if I have the inner cylinder. in this way I can generate mesh using cooper method however, without inner cylinder the geometry is different and whatever I tried I couldn't generate mesh.

Amir,

Regards.

Milind Khedkar December 29, 2008 03:25

Re: MRF problem
 
I do agree with Yasser. No need to generate two different cylinders. Give MRF only to one cylinder. Milind..

Amir December 29, 2008 09:19

Re: MRF problem
 
Dear Milind,

I would like to ask if the size of cylinder affects the results!

Regards.

Amir

Milind Khedkar December 29, 2008 10:04

Re: MRF problem
 
No. The size of the cylinder will not affect the results if there is no stationary part enveloped within it. Also you can extend the outer boundary of the cylinder a bit. You have to maintain it as close as possible.

Milind..

Amir December 30, 2008 09:11

Re: MRF problem
 
Dear Milind Khedkar,

Thanks for your respond. I will try again to see how far the results will change.

I would like to ask also the differences between MRF and Moving Mesh, and if I should use the Moving mesh instead of MRF.

I appreciate your concentration.

Amir.


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