# couple and spin index

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 July 7, 2004, 06:52 couple and spin index #1 novice Guest   Posts: n/a Hi Experts, Can I have couple in between two cells which have different spin indices. They are in partial overlapping. In userguide it is written that couple is not possible when cells have different spin or/and porocity indices, and also between fluid and solid cells. Since couple between fluid and solid cells is possible I took doubt on former also. So please guide how to give couple between cells with different spin indices. Thanks a lot.

 July 7, 2004, 06:58 Re: couple and spin index #2 4xF Guest   Posts: n/a As stated in the manual, you cannot have couples between two cells having different spin indices.

 July 7, 2004, 07:37 Re: couple and spin index #3 Thomas Guest   Posts: n/a and you have couples between solid and fluids but no partial couples, this will not work!

 July 7, 2004, 07:48 Re: couple and spin index #4 Richard Guest   Posts: n/a The only way to join two cells with different spin indices is MRF. If the cell faces match 1:1 (no couple required) then you can choice implicit MRF or boundary-coupled explicit MRF. If the cells don't match 1:1, you need region-coupled explicit MRF. This isn't a subject you should wander into by accident, it's quite complicated, so be sure you need this functionality before you start work on it.

 July 7, 2004, 08:07 Re: couple and spin index #5 novice Guest   Posts: n/a Thanks for replies. But in case of explicit MRF it asks for material no. I have only one material (fluid), but part of it is rotating and part is not rotating. As far as I know we can not have two material numbers with same properties. In case of 1:1 matching there is absolutely no problem, since we can give different spin indeces and use implicit MRF. I am still unanswered how to sort out my problem: Coupling between nonmatching fluid meshes which have different speeds. (one is stationary and other is rotating). Thanks in advance.

 July 7, 2004, 08:50 Re: couple and spin index #6 4xF Guest   Posts: n/a As Richard stated, you have to use regionwise coupled MRF (see manual for details, since only certain type of region combinations are allowed, e.g. inlet/pressure).

 July 8, 2004, 03:31 Re: couple and spin index #7 Richard Guest   Posts: n/a There's no reason why you can't have two materials with the same properties: that is exactly what is required for explicit MRF. In implicit MRF, the rotation is specified by spin index, in explicit MRF it is specified by material index.