# cg_omega

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 May 11, 2005, 17:54 cg_omega #1 mehrdad Guest   Posts: n/a hi I want to write a Udf for rotating a circle in a 2d problem. anybody can help me? please give me a example udf thanks

 May 12, 2005, 07:46 Re: cg_omega #2 Jason Guest   Posts: n/a I don't know anything about UDFs, but if you're trying to spin the circle at a constant rate, I wouldn't bother with UDFs. You can define a rotation in the boundary conditions. Depending on your model, you can either define the fluid zone as rotating, and the wall as stationary relative to the zone (it's not the fluid that rotates, it's the computational domain of the fluid that you are rotating, which usually saves time on the number of iterations you need to complete... the trick is to define the fluid zone as rotating in the SAME direction that the wall would rotate, not the opposite direction as you would think if you were rotating the medium), or just the wall as rotating. If it's not actually a cylinder, you could use sliding meshes instead. Just a thought, and this will not help if you aren't spinning at a constant rate. Hope this helps, and good luck, Jason

 May 12, 2005, 09:44 Re: cg_omega #3 mehrdad Guest   Posts: n/a hi jason thanks but i wanna to rotate a circle, that it has a blade in its circumstance, then i can't rotate it by boundary condition panel. i want to write a udf for it.i want to use rigid body motion udf for it. good luck'

 May 12, 2005, 10:20 Re: cg_omega #4 Luca Guest   Posts: n/a Use sliding mesh or write a UDF with cg_motion. Look for MRF in the guide, you can use if I undestand well your problem.Luca

 May 12, 2005, 11:08 Re: cg_omega #5 mehrdad Guest   Posts: n/a Hi luca thanks I want a typical udf for just, rotation of a 2d body. for rotation a 2d body which of the cg_omega(1) or cg_omega(2) or cg_omega(3) must equal to omega. can i use time depended omega in rigid body motion udf? thanks my friend

 May 13, 2005, 02:54 Re: cg_omega #6 Luca Guest   Posts: n/a yes sure!you can write a udf and set an angular velocity variable in time. Luca

 May 13, 2005, 03:43 Re: cg_omega #7 mehrdad Guest   Posts: n/a Hi luca thanks for ur help luca can u send to me a typical udf for just angular velocity moving of a rigid body? now,i can move a rigid body in one direction with time depended velocity,but i can not rotate it. i want a example udf for rotating of a rigid body only not linear velocity. good luck

 May 13, 2005, 03:47 Re: cg_omega #8 Luca Guest   Posts: n/a Hi! unfortuantely I dont' use cg_motion for my job. Anyway have a look at Fluent's UDF guide. there's a simple example of a cg_motion UDF. To define an angular velocity you need to modifiy the variable omega which is an input of cg_motion macro.Luca

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