# rigid body motion with constant velocity

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 August 12, 2014, 17:43 rigid body motion with constant velocity #1 Member   aliali Join Date: Apr 2014 Posts: 35 Rep Power: 4 Hi I need to put a constant velocity on my rigid body in one direction. but I don't know where and how I have to do it? thanks

 August 12, 2014, 18:56 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 12,831 Rep Power: 100 Is it an immersed solid or a moving mesh rigid body? Does the degrees of freedom controls do what you want? If you have a rigid body in constant motion then it is not really rigid body motion and really just a moving mesh model. So you could just model it with moving mesh (or a pre-defined source term) ghoroobeaakhar likes this.

 August 13, 2014, 05:59 #3 Member   aliali Join Date: Apr 2014 Posts: 35 Rep Power: 4 Thanks. I put one degree of freedom for it so It moves only in one direction. I first simulate the body under gravity force and I got results but now I want to simulate the same body with a constant velocity (3 m/s) in the same direction. I defined a rigid body and a wall condition for the surfaces of my rigid body. In rigid body options I have an initial velocity and in wall condition's option I have specified displacement ans specified location. I tried to set specified displacement as 3[m]*t but it doesn't work. how can I say to my rigid body that moves all the time in 3 m/s?

 August 13, 2014, 06:07 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 12,831 Rep Power: 100 Try defining an initial velocity of 3m/s and give it a massive mass. Then the fluid forces acting on it will not affect it. acasas and ghoroobeaakhar like this.

 August 14, 2014, 14:50 #5 Member   aliali Join Date: Apr 2014 Posts: 35 Rep Power: 4 Thanks ghorrocks I have another question. I defined wall condition for the surfaces of my rigid body and I need to calculate the velocity of the wall. I want to check that the wall is moving at 3 m/s . In fact how can I know the velocity of the wall at every moment and acceleration of that? Thanks

 August 14, 2014, 18:30 #6 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 12,831 Rep Power: 100 Have a look at the reference manual. It lists all the variables available on rigid bodies.

August 20, 2014, 10:53
#7
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hamid
Join Date: Nov 2009
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Quote:
 Originally Posted by ghoroobeaakhar Thanks ghorrocks I have another question. I defined wall condition for the surfaces of my rigid body and I need to calculate the velocity of the wall. I want to check that the wall is moving at 3 m/s . In fact how can I know the velocity of the wall at every moment and acceleration of that? Thanks

by output setting in cfx-pre or timestep selector in post or chart(transient xy....)

December 23, 2014, 15:52
#8
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Antonio Casas
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Quote:
 Originally Posted by ghorrocks Try defining an initial velocity of 3m/s and give it a massive mass. Then the fluid forces acting on it will not affect it.

Is it initial velocity set in Dynamic Mesh Zones/ Motion Attributes/Center of Gravity Velocity ?

I´m working under Fluent
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 December 23, 2014, 17:28 #9 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 12,831 Rep Power: 100 This is the CFX forum. Try the fluent forum.

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