Hi all,

I am trying to rotate a geometry using an UDF file which provides the function: DEFINE_CG_MOTION.

I have a cylinder which is rotated 15 deg about the x-axis. I want to rotate it as a solid body. The real geometry is much more complicated, and I need to use dynamic meshing, which is why I need the CG_MOTION UDF.

In the UDF I use the statement:

NV_D(cg_omega, =, omega_x, omega_y, omega_z);

If I just provide omega_z, the entire cylinder rotates about the z-axis, naturally. If I want the cylinder to rotate at any given angular frequency, omega, I multiply omega with a unit vector which points along the length of the cylinder. This doesn't work. The cylinder just rotates around its Center of Gravity point by the values given in cg_omega, and not using it as a rotational vector, with the rotation perpendicular to it.

I tried to adjust the 'Center of Gravity Orientation' in the 'Dynamic Mesh Zones' panel, but this has no effect.

Heeelp

Best regards Mads

[almostafa67]

hi dear mads...
long ago you were studying a case that contained rotating a cylinder about z axis,now i'm working on something like that,i sent you two images that both of them are kind of peristaltic pump,i want to rotate two/one small cylinder about z axis,i should write an udf but actually i dont know which command can make yhis simple movement for me,i will be thankful if you could help me out
looking forward to ur help.

[M MOHSIN]

hi , i needed help to do a cfd of a rotating propeler . i need a udf for it. anybody plz help me out here. looking forward