DYNAMIC MESH udf for orbiting motion.

avidash · March 4, 2015, 07:37

I am trying to write an UDF for orbiting motion eg as in this picture in the dynamic mesh method
motion.gif

the body(square) has no omega of its own, but it is translating in a circle of radius (say 10 cm ) with some angular velocity ( say 1 rad/sec).

avidash · March 4, 2015, 07:40

will appreciate any help...

pakk · March 4, 2015, 09:00

Start with an empty text file, look in the Fluent help for which functions you can use, and just try something. If you think you have something reasonable, try to compile it and test it. If it does not work, and you need help, post your attempt here and I am sure you will get some advice. Good luck!

avidash · March 4, 2015, 10:58

Thanks for the interesting reply.
Here is what i know.
The following macro is used to define the zone motion
" DEFINE_CG_MOTION (name, dt, vel, omega, time, dtime) "
where vel & omega are linear & angular velocity of the zone (assuming it to be a rigid body).

But in an orbiting motion the body itself has no omega, but is translating in a circular motion with some angular velocity. I haven't been able to figure out how to give the CG (centre of gravity) an angular velocity about the global frame of reference.

PS : defining velocity of CG as V-x_component = V*sin(wt) & V-x_component = V*cos(wt) isn't a very acurate way.

March 4, 2015, 07:37	DYNAMIC MESH udf for orbiting motion.	#1
avidash New Member Avinash Dash Join Date: Dec 2014 Location: Bangalore, India Posts: 4 Rep Power: 11	I am trying to write an UDF for orbiting motion eg as in this picture in the dynamic mesh method motion.gif the body(square) has no omega of its own, but it is translating in a circle of radius (say 10 cm ) with some angular velocity ( say 1 rad/sec).

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March 4, 2015, 07:40		#2
avidash New Member Avinash Dash Join Date: Dec 2014 Location: Bangalore, India Posts: 4 Rep Power: 11	will appreciate any help...

March 4, 2015, 09:00		#3
pakk Senior Member Join Date: Nov 2013 Posts: 1,965 Rep Power: 26	Start with an empty text file, look in the Fluent help for which functions you can use, and just try something. If you think you have something reasonable, try to compile it and test it. If it does not work, and you need help, post your attempt here and I am sure you will get some advice. Good luck!

March 4, 2015, 10:58		#4
avidash New Member Avinash Dash Join Date: Dec 2014 Location: Bangalore, India Posts: 4 Rep Power: 11	Thanks for the interesting reply. Here is what i know. The following macro is used to define the zone motion " DEFINE_CG_MOTION (name, dt, vel, omega, time, dtime) " where vel & omega are linear & angular velocity of the zone (assuming it to be a rigid body). But in an orbiting motion the body itself has no omega, but is translating in a circular motion with some angular velocity. I haven't been able to figure out how to give the CG (centre of gravity) an angular velocity about the global frame of reference. PS : defining velocity of CG as V-x_component = Vsin(wt) & V-x_component = Vcos(wt) isn't a very acurate way.