[schlappeseppel124]

Hello All,

i got a problem concerning 6dof and UDF. I got a 3D case and would like to move a valve by the pressure, that is generated by a moving wall.

For the 6dof moving of the valve i used the following UDF:

#include "udf.h"
#include "math.h"


DEFINE_SDOF_PROPERTIES(Valve_6dof, prop, dt, time, dtime)
{
prop[SDOF_MASS] = 1.645e-8;
prop[SDOF_IXX] = 6.04e-15;
/*The values for mass and moment of inertia are very low because the valve is very small.*/

prop[SDOF_ZERO_TRANS_X] = TRUE;
prop[SDOF_ZERO_TRANS_Y] = TRUE;
prop[SDOF_ZERO_TRANS_Z] = TRUE;

prop[SDOF_ZERO_ROT_X] = FALSE;
prop[SDOF_ZERO_ROT_Y] = TRUE;
prop[SDOF_ZERO_ROT_Z] = TRUE;

/*The case is symmetric in x-direction.*/
prop[SDOF_SYMMETRY_X] = 1;
prop[SDOF_SYMMETRY_Y] = 0;
prop[SDOF_SYMMETRY_Z] = 0;

Message("6dof updated);

https://picload.org/image/rdpaapao/cfd.png

But the valve is not mooving at all.
1. As you can see in the picture i would like to rotate the valve around a certain point. Do I need to add that somehow?

2. Do i need to add the moment of inertia for SDOF_IYY and SDOF_IZZ because it is 3D or can i neglect it because it is only rotaiting around the x-axis.

3. The moment of inertia i calculated using the Steiner's theorem because it shall rotate not around the center but the point marked in the picture. Or do i need to link it to the cordinate system of the whole body?

Any help is appreciated. If you need any further information please let me know.

Thank you very much

[schlappeseppel124]

Is it possible that it has something to do with the inertia? That my inertia is too low like it is in this case?

http://www.cfd-online.com/Forums/flu...eleration.html

[schlappeseppel124]

And can anybody tell me what this message means:

6DOF angular solver has not converged

I could not find anything in the cfd-board or even the internet concerning this.

Thank you very much

[rsaurabh]

Hi,
Have you got the solution for your problem. i am also working on same type case where center of rotation is different from C.G of body. If possible we can work together.
i will be happy to share what i know.
Thanks.
Saurabh

[schlappeseppel124]

Hey rsaurabh,

sorry for the late answer, no I did not solve my problem. I worked around the valve by simulating it with boundary conditions. But if u find out something new, it would be nice if you can share it here.

[rsaurabh]

Hi schlappeseppel124,
Try using ANSYS 17.2 or above. in those versions 6DOF setting is easy to manage. You have both options there, either do 6DOF setting in setting your case else use UDF. i have implied my setting while setting my case.

I hope this will help.

[alleau]

Hi all,

The new setup of SDOF solver in fluent v17 is more understandable as rsaurabh said. However, you can define it on older versions as well.

The rotation center of a solid body is described as CG in Fluent.
Go to dynamic mesh, create/edit dynamic mesh zone, and rigid body for your moving solid. There are coordinates for the centre gravity location, if you enable Six DOF option.

Rotation will then be defined from this point.

Hope this help !

[diggee]

Originally Posted by rsaurabh

Hi,
Have you got the solution for your problem. i am also working on same type case where center of rotation is different from C.G of body. If possible we can work together.
i will be happy to share what i know.
Thanks.
Saurabh

Hi Saurabh, did you manage to figure out how to rotate about a point different from the center of gravity? Please do let me know if you did, need help urgently!