CFD Online Discussion Forums - 2 degree of freedom in one direction UDF

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2 degree of freedom in one direction UDF

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

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

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