How to set initial velocity for rigid body motion?

pbachant · May 14, 2017, 09:25

I am trying to simulate an object decelerating from fluid forces, but it's unclear how to set the initial velocity and point displacement fields for the boundary of interest. I assume the point displacement needs to be calculated, so I am using that for the patch of interest, but the initial value doesn't appear to have an effect, i.e., the motion solver is simply predicting no force or motion. Is there a setting in the motion solver for specifying the initial velocity?

pbachant · May 14, 2017, 19:06

The answer was pretty simple, but maybe a little misleading. Initial velocity can be set with:

Code:

sixDoFRigidBodyMotionCoeffs
{
    velocity (0 0 -1.5);
}

It should probably be called something like initialVelocity though. These values are read by the sixDoFRigidBodyMotionState object.

taalf · March 27, 2020, 08:01

Hi all,

What about initial angular velocity ?...

taalf · March 27, 2020, 08:18

Quote:

Originally Posted by taalf

Hi all,

What about initial angular velocity ?...

Oh, yes, through the angularMomentum entry, eg.:

momentOfInertia (100 100 100);
angularMomentum (0 0 78.54);

The angular momentum

equals $I.\omega$ , with

the moment of inertia given above (entry "momentOfInertia"), and $\omega$ the desired angular velocity in [rad/s].

May 14, 2017, 09:25	How to set initial velocity for rigid body motion?	#1
pbachant Senior Member Pete Bachant Join Date: Jun 2012 Location: Boston, MA Posts: 173 Rep Power: 13	I am trying to simulate an object decelerating from fluid forces, but it's unclear how to set the initial velocity and point displacement fields for the boundary of interest. I assume the point displacement needs to be calculated, so I am using that for the patch of interest, but the initial value doesn't appear to have an effect, i.e., the motion solver is simply predicting no force or motion. Is there a setting in the motion solver for specifying the initial velocity? __________________ Home \| Twitter \| GitHub

May 14, 2017, 19:06		#2
pbachant Senior Member Pete Bachant Join Date: Jun 2012 Location: Boston, MA Posts: 173 Rep Power: 13	The answer was pretty simple, but maybe a little misleading. Initial velocity can be set with: Code: sixDoFRigidBodyMotionCoeffs { velocity (0 0 -1.5); } It should probably be called something like initialVelocity though. These values are read by the sixDoFRigidBodyMotionState object. zkdkeen and amanbearpig like this. __________________ Home \| Twitter \| GitHub

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March 27, 2020, 08:01		#3
taalf Member William Tougeron Join Date: Jan 2011 Location: Czech Republic Posts: 70 Rep Power: 15	Hi all, What about initial angular velocity ?...