# 2 degree of freedom in one direction UDF

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 March 3, 2014, 11:24 2 degree of freedom in one direction UDF #1 New Member   Linh Tuan The Nguyen Join Date: Nov 2012 Posts: 9 Rep Power: 4 Hi, I am doing simulation for flow around free oscillating cylinder. The cylinder was attach with the mass by spring which can be consider as 2 DOF system in one direction (y direction) not 1DOF for each (x, y direction). I using SDOF in Fluent for single degree of freedom case and it was working fine. But when it's come to 2 DOF, I have no idea how to start. I am very grateful if anybody can give me some suggestion how to start. Best Regards

 March 5, 2014, 06:53 #2 Senior Member     Daniele Join Date: Oct 2010 Location: Italy Posts: 918 Rep Power: 15 You can use the 6dof solver and create an udf with body properties and use the following lines to have restricted motion: Transational motion in x direction is not allowed: Code: `prop[SDOF_ZERO_TRANS_X] = TRUE;` Transational motion in x direction is allowed: Code: `prop[SDOF_ZERO_TRANS_X] = FALSE;` Transational motion in y direction is not allowed: Code: `prop[SDOF_ZERO_TRANS_Y] = TRUE;` Transational motion in y direction is allowed: Code: `prop[SDOF_ZERO_TRANS_Y] = FALSE;` Transational motion in z direction is not allowed: Code: `prop[SDOF_ZERO_TRANS_Z] = TRUE;` Transational motion in z direction is allowed: Code: `prop[SDOF_ZERO_TRANS_Z] = FALSE;` Rotational motion around x axis is not allowed: Code: `prop[SDOF_ZERO_ROT_X] = TRUE;` Rotational motion around x axis is allowed: Code: `prop[SDOF_ZERO_ROT_X] = FALSE;` Rotational motion around y axis is not allowed: Code: `prop[SDOF_ZERO_ROT_Y] = TRUE;` Rotational motion around y axis is allowed: Code: `prop[SDOF_ZERO_ROT_Y] = FALSE;` Rotational motion around z axis is not allowed: Code: `prop[SDOF_ZERO_ROT_Z] = TRUE;` Rotational motion around z axis is allowed: Code: `prop[SDOF_ZERO_ROT_Z] = FALSE;` Daniele linh nguyen likes this.

March 7, 2014, 06:50
#3
New Member

Linh Tuan The Nguyen
Join Date: Nov 2012
Posts: 9
Rep Power: 4
Thank Daniele,

I have used this SDOF Macro already for Single degree of cylinder system I have done before and I quite familiar with SDOF Macro. But now I am doing 2DOF in 1 direction, that, the cylinder in the flow domain will be attached with a Mass (see attachment). Do you think in Fluent they have a Macro for this or I have to write my own UDF for this case.

Linh
Attached Images
 2DOF.jpg (12.1 KB, 25 views)

 Tags cylinder, dynamic mesh

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