# Problem with a rotating problem

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 June 24, 2012, 23:54 Problem with a rotating problem #1 New Member   Sam Join Date: May 2012 Posts: 8 Rep Power: 6 Hi, I'm trying to solve the following problem: I have a rotating cylinder with a constant speed. For that I have define 2 fluid regions, one surrounding the cylinder and the other one with the rest. I tried to solve MRF impossing to the fluid zone surrounding the cylinder the angular velocity and impossing the cylinder (wall) BC of moving wall relative to adjacent zone. The problem is that I don't think that is actually working because I obtained the same results if I impose or no velocity for the surrounding fluid. Is possible that the problem come that the "Mesh Interfaces" option is deactivated in Fluent? I have also tried with a "steady" solution trying with an udf but I also can't make it worked. Can anyone help me?

June 25, 2012, 02:28
#2
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Sijal
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Quote:
 Originally Posted by samolcue Hi, Situation1: I tried to solve MRF impossing to the fluid zone surrounding the cylinder the angular velocity and impossing the cylinder (wall) BC of moving wall relative to adjacent zone. Situation 2:The problem is that I don't think that is actually working because I obtained the same results if I impose or no velocity for the surrounding fluid. Can anyone help me?
Because if you giving the inner wall (cylinder) as moving wall relative to adjacent zone, which means you are specifying no motion at all and it is similar to situation 2. Just think that you are measuring the giving the velocity to train and the person on the platform. This mean that the person is also moving with you including the platform. Another query, what velocity you are giving to wall? -ve and equal or +ve and equal?

So either give the velocity to the wall or fluid. Best way is to give velocity to fluid to solve the equations in rotating reference frame. Make sure that the cylinder centre is placed at origin.

June 25, 2012, 11:38
#3
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Sam
Join Date: May 2012
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Quote:
 Originally Posted by Far Because if you giving the inner wall (cylinder) as moving wall relative to adjacent zone, which means you are specifying no motion at all and it is similar to situation 2. Just think that you are measuring the giving the velocity to train and the person on the platform. This mean that the person is also moving with you including the platform. Another query, what velocity you are giving to wall? -ve and equal or +ve and equal? So either give the velocity to the wall or fluid. Best way is to give velocity to fluid to solve the equations in rotating reference frame. Make sure that the cylinder centre is placed at origin.
I have tried a lot of different things and at all I'm not able to make the cylinder move:
-BC moving wall for the cylinder with rotational speed
-MRF giving speed for the fluid zone
-Dynamic mesh with and udf for the cylinder

And I don't know why any of this is working.

I think that now is not important the sign of the velocity, because first I want just to make it move, doesn't care if is clockwise or inverse.

The origin is at the center also.

I've followed the MRF tutorial in fluent but I don't have the Mesh Interfaces option activated, and I'm beginning to think that maybe is here the problem. Is that possible?

June 25, 2012, 14:08
#4
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Sijal
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Quote:
 I've followed the MRF tutorial in fluent but I don't have the Mesh Interfaces option activated, and I'm beginning to think that maybe is here the problem. Is that possible?
Indeed it is

 June 25, 2012, 22:27 #5 New Member   Sam Join Date: May 2012 Posts: 8 Rep Power: 6 As I have put on the Freelancers forum, if anybody is able to check what I have done and teach me how to solve it properly, I'm disposed to pay.

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