# MRF: how to validate of to know if things were set up correctly?

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 March 27, 2012, 15:25 MRF: how to validate of to know if things were set up correctly? #1 Senior Member   lore Join Date: Mar 2010 Location: Italy Posts: 460 Rep Power: 11 Hi all; I'm simulating a spinning wheel with MRFSimpleFoam… How would you check if my setup was correct?

 August 11, 2012, 21:34 #2 New Member   Dogan Join Date: May 2010 Posts: 8 Rep Power: 9 the easy way to validate is to find same study and after compare them... this is the acadamic way to validate...

 December 14, 2012, 09:21 #3 Member   Aathavan Join Date: Nov 2012 Posts: 70 Rep Power: 6 Hi Lovecraft22, I am doing simulation of fan, I want to check case setup. I want to conform my MRFZone file, I am bit confused. the axis of rotation is (0 0 1), origin (0 0 0 ) // how can we conform it? omega 78.54 // is it should be - or +, for + setting I am not at all getting result. for - RPM the result deviates 40%. can you please suggest what should i do? Thanks, Aadhavan

 December 14, 2012, 14:33 #4 Senior Member   lore Join Date: Mar 2010 Location: Italy Posts: 460 Rep Power: 11 Hi Aadhavan; I'm not sure I actually understood your question. Btw, you need to specify: 1. your axis direction, for instance (0 0 1) if you want your axis direction to be aligned with the z-direction (meaning you body will rotate along this direction) 2. you axis origin, meaning the point your body will be rotating around, for instance (1 1 0), meaning that point will be located at those coordinates. Of course, if your axis direction is (0 0 1) then you can set whatever you want for the origin z coordinate as it will not matter. 3. omega, is the angular velocity at which your body rotates. It is chosen according the the right hand rule: point your thumb in the same direction as the axis and then your fingers will give you the positive direction for the velocity. Hope this helps

 December 17, 2012, 05:46 #5 Member   Aathavan Join Date: Nov 2012 Posts: 70 Rep Power: 6 Hi Lovecraft22, Thanks for your reply, it seems that my settings are correct, but I dont know what factor is blocking the fan static pressure raise. I am getting only 40Pa static pressure raise but it should be 200Pa. I spend more than 2 months for this issue, still I am not able to figure out the problem. Thanks, Aadhavan Last edited by Aadhavan; December 18, 2012 at 04:27.

 December 17, 2012, 15:11 #6 Senior Member   lore Join Date: Mar 2010 Location: Italy Posts: 460 Rep Power: 11 It can be due to a large number of things, one could be the mesh on the fan (and on the surrounding region) for instance.

 January 2, 2013, 23:44 #7 Member   Jianye Xia Join Date: Mar 2009 Posts: 32 Rep Power: 10 Hi, lovecraft22, what is the dimension of omega? [rad/s] or [rpm]?

 January 3, 2013, 03:55 #8 Senior Member   lore Join Date: Mar 2010 Location: Italy Posts: 460 Rep Power: 11 Usually it should be rad/s otherwise you can change its units to be whatever you like.

 January 11, 2013, 18:38 #9 Member   Join Date: Jun 2012 Posts: 73 Rep Power: 7 I use paraview to check if my MRF zone is set up properly. Just display the velocity vectors of the rotating walls. So you can check direction and magnitute of the rotational velocity easily.

January 11, 2013, 20:21
#10
Member

Jianye Xia
Join Date: Mar 2009
Posts: 32
Rep Power: 10
Quote:
 Originally Posted by lovecraft22 Usually it should be rad/s otherwise you can change its units to be whatever you like.
Thanks lovecraft22, I have checked this in the development of U eqn in Rotating Frame, it showed that the omega's dimension should be rad/s.

 October 30, 2016, 07:50 MRF-Stirrer Tank #11 New Member   rezanobakht Join Date: Sep 2014 Posts: 4 Rep Power: 4 Hi I'm Simulating an agitating tank (Rushton Turbine Impeller). I create the geometry in Gambit and imported it in OpenFOam then I tried to run the Case and after a while I did it. But there is a big problem and it make me confused. after running I check the velocity profile and I find out that the velocity is more higher than the real velocity. for example my omega is 100 and the radius of my impeller is 12 cm and the result of openFoam shows the velocity 22000 m/s !!!!!!!!!! please help me.

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