yade-users team mailing list archive
-
yade-users team
-
Mailing list archive
-
Message #02904
Re: TranslationEngine Vs JumpChangeSe3
2010/4/25 Václav Šmilauer <eudoxos@xxxxxxxx>
>
> > both TranslationEngine and JumpChangeSe3 work if bodies are dynamic.
> > Now I tried a simple sphere-sphere interaction test using the basic
> > Law2_ScGeom_FrictPhys_Basic() law. One ball is fixed, the other one is
> > moved by using JumpChangeSe3 (setting setVelocities to true). The only
> > thing I notice is that although no damping is present, the moving ball
> > gets the rest at equilibrium (just run the attached script and press
> > F8 to see what I mean, you will see the contact normal force getting a
> > constant value).
> > If I try the same test but using ForceEngine (now it is commented in
> > the attached file but you can try to use it while commenting out
> > JumpChangeSe3) I get the expected result, the moving ball is bouncing
> > around the equilibrium (again just run the script and press F8).
> >
> > Nothing wrong, I just wuold like to understand (and maybe you can help
> > me) why in displacement control I do not any bouncing around the
> > equilibrium. Is not the same as applying a body force according to the
> > code?
>
> I think the result it right. ForceEngine will apply force, which will
> end up in sum with repulsive/attractive force between particles. The
> equilibrium position will be moved by ForceEngine, but you will still
> observe oscillation as if without ForceEngine.
>
> For JumpChangeSe3, particle is displaced by delta at every step. The
> equilibrium ("constant" position) will come at the moment when
> displacement by JumpChangeSe3 will be exactly compensated by
> displacement by NewtonIntegrator later in the same step. That's how I
> would explain the "equilibrium".
>
Hi Vaclav,
I am not entirely happy with this. I think the result is correct, the code
does what we say to do. However, dose this mean that if you apply an initial
velocity to the body, instead of a force, the coefficient of restitution
would be zero? Sorry if I guess, thanks for comments.
Chiara
>
> Let me know it it makes sense, I will have a look a little bit more
> otherwise -- no problem.
>
> Cheers, v.
>
>
>
>
>
> _______________________________________________
> Mailing list: https://launchpad.net/~yade-users<https://launchpad.net/%7Eyade-users>
> Post to : yade-users@xxxxxxxxxxxxxxxxxxx
> Unsubscribe : https://launchpad.net/~yade-users<https://launchpad.net/%7Eyade-users>
> More help : https://help.launchpad.net/ListHelp
>
Follow ups
References