# Body to rotate by action of the air flow

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 June 16, 2010, 08:39 Body to rotate by action of the air flow #1 New Member   Roberto Pravata Join Date: Jun 2010 Posts: 3 Rep Power: 9 Hi all, I need your help How can I do for a body to rotate by action of the air flow? I want to know the speed of rotation as a function of air velocity. Do I have to do with "moving reference frame model? or "rigid body motion model? Many thanks.

 June 16, 2010, 11:29 #2 Senior Member   Join Date: Apr 2009 Posts: 129 Rep Power: 10 What you need to use to accomplish your goal is the "6-DOF Motion Model." You can then setup reports to monitor rotation rate. Since this is a complicated model, I suggest you read all the help documentation and practice on very simple geometry first.

 June 27, 2010, 14:31 #3 New Member   Roberto Pravata Join Date: Jun 2010 Posts: 3 Rep Power: 9 THANKS!!! but one more question how do I put up resistance to rotation. thank you very much

 June 28, 2010, 11:38 #4 Senior Member   Join Date: Apr 2009 Posts: 129 Rep Power: 10 HELP > Modeling > Modeling Dynamic Fluid Body Interaction > Working with 6-DOF Bodies > What are External Forces and Moments? > Adding an External Force or Moment Read the help file, there's a damping moment, and a damping force you can add.

 June 29, 2010, 10:19 #5 New Member   Roberto Pravata Join Date: Jun 2010 Posts: 3 Rep Power: 9 Yes, thank very much. You are the Best. From Spain realy thanks.

August 9, 2010, 16:31
#6
New Member

Rafael Oliveira
Join Date: Mar 2010
Posts: 6
Rep Power: 9
Hi rpravata,

Do you had success in simulation? Here, I have a channel (2D) with a square in the middle and I'd like to simulate the rotate this object by action of the fluid flow. I've been using a 6DOF udf together with dynamic mesh, but when I run the solver after some iterations appear the following error: Warning: negative volume detected --> repeat smoothing!
I've tried decrease the time step, but the error persists. Following below the udf that I've been using:

include "udf.h"

{
prop[SDOF_ZERO_TRANS_X] = TRUE;
prop[SDOF_ZERO_TRANS_Y] = TRUE;
prop[SDOF_ZERO_TRANS_Z] = TRUE;
prop[SDOF_ZERO_ROT_X] = TRUE;
prop[SDOF_ZERO_ROT_Y] = TRUE;

/* Define the mass matrix */

prop[SDOF_MASS] = 1;
prop[SDOF_IXX] = 0.25;
prop[SDOF_IYY] = 0.25;
prop[SDOF_IZZ] = 0.50;

printf ("\n2d_test_box: Updated 6DOF properties");
}

Quote:
 Originally Posted by rpravata Hi all, I need your help How can I do for a body to rotate by action of the air flow? I want to know the speed of rotation as a function of air velocity. Do I have to do with "moving reference frame model? or "rigid body motion model? Many thanks.

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