# MRF problem

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 December 15, 2008, 09:59 MRF problem #1 Amir Guest   Posts: n/a 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.

 December 16, 2008, 08:57 Re: MRF problem #2 Magic Guest   Posts: n/a 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

 December 17, 2008, 15:44 Re: MRF problem #3 Amir Guest   Posts: n/a 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

 December 17, 2008, 21:57 Re: MRF problem #4 Yasser Selima Guest   Posts: n/a 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.

 December 18, 2008, 09:17 Re: MRF problem #5 Amir Guest   Posts: n/a 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.

 December 29, 2008, 03:25 Re: MRF problem #6 Milind Khedkar Guest   Posts: n/a I do agree with Yasser. No need to generate two different cylinders. Give MRF only to one cylinder. Milind..

 December 29, 2008, 09:19 Re: MRF problem #7 Amir Guest   Posts: n/a Dear Milind, I would like to ask if the size of cylinder affects the results! Regards. Amir

 December 29, 2008, 10:04 Re: MRF problem #8 Milind Khedkar Guest   Posts: n/a 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..

 December 30, 2008, 09:11 Re: MRF problem #9 Amir Guest   Posts: n/a 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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