Drift in Sinusoidal Rigid Body Motion with Two Domains

dae4god · September 22, 2012, 04:17

Does anyone know why the CFX Rigid Body solver only accepts Torque values above a certain threshold number? This threshold number also seems to depend on the timestep size.

ghorrocks · September 24, 2012, 22:59

This sounds very strange. Can you give more details - what torque numbers are you trying to enter? What are you modelling?

dae4god · September 24, 2012, 23:45

Hi ghorrocks,

I actually started a new thread with a title that was more appropriate to the problem - sorry. The new thread is at http://www.cfd-online.com/Forums/cfx...tml#post383433.

My simulation involves rotating a rigid body at very small angular accelerations of the order of $\alpha = 4.18\times 10^{-3} rad s^{-2}$ . However, when I look at the Angular Acceleration Z in one of the CFD-Solver monitors, it shows $\alpha = 0 rad s^{-2}$ .

Do you know why this happens, or how I can rotate my rigid body at small angular accelerations?

September 22, 2012, 04:17	Rigid Body Solver Input	#1
dae4god New Member Josh Yen Join Date: Jul 2011 Posts: 14 Rep Power: 15	Does anyone know why the CFX Rigid Body solver only accepts Torque values above a certain threshold number? This threshold number also seems to depend on the timestep size. Last edited by dae4god; September 23, 2012 at 23:20.

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September 24, 2012, 22:59		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,852 Rep Power: 144	This sounds very strange. Can you give more details - what torque numbers are you trying to enter? What are you modelling?

September 24, 2012, 23:45		#3
dae4god New Member Josh Yen Join Date: Jul 2011 Posts: 14 Rep Power: 15	Hi ghorrocks, I actually started a new thread with a title that was more appropriate to the problem - sorry. The new thread is at http://www.cfd-online.com/Forums/cfx...tml#post383433. My simulation involves rotating a rigid body at very small angular accelerations of the order of $\alpha = 4.18\times 10^{-3} rad s^{-2}$ . However, when I look at the Angular Acceleration Z in one of the CFD-Solver monitors, it shows $\alpha = 0 rad s^{-2}$ . Do you know why this happens, or how I can rotate my rigid body at small angular accelerations?