# yade-users team mailing list archive

## Re: question about clump?

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```
thank you for the reply!

at the begining the clumps have both rotational and translational motion, but later the rotational motion finish and just have translational motion. at this time I found the clump slip on the plane in a curve. I think its trajectory should slip in a line, because there is no rotational motion and just have translational motion.

Jingsong

> From: eudoxos@xxxxxxxx
> Date: Fri, 5 Jun 2009 22:02:48 +0200
> Subject: Re: [Yade-users] question about clump?
>
> What's the problem there? The new clump collides with the other clump
> getting some rotational motion, then different spheres hit the ground at
> different points which makes its trajectory bend towards the side of
> contact, as there is shear. Did I miss something?
>
> Vaclav
>
> > Hello, everyone, sorry to bother you again!
> > First thank Vaclav for the reply about box interaction. Vaclav
> > suggested me "replacing box by a few clumped spheres would be good
> > enough for your purposes."
> > These days I try to learn how to use clump as the example in
> > yade(ClumpTestGen), but i noticed there seems exist some unreasonable
> > movement in the shear direction when I generated more some clumps in the
> > example(ClumpTestGen). is it because of the interaction between clumps?
> >
> > I just make the plane bigger and add two more clumps as follow:
> >
> > shared_ptr<Body>
> > ground=Shop::box(Vector3r(0,0,-1),Vector3r(10,10,.2));
> >
> > // three-sphere clump
> > clumpPos=Vector3r(0.5,2.5,2);
> > relPos.push_back(Vector3r(0,-.5,.5)); radii.push_back(.5);
> > relPos.push_back(Vector3r(0,.5,0)); radii.push_back(.5);
> > relPos.push_back(Vector3r(.5,0,0)); radii.push_back(.5);
> > relPos.clear(); radii.clear();
> >
> > // four-sphere clump (this one seems have abnormal movement,
> > horizontal translation in a curve (not a line) on the plane after
> > interaction)
> > clumpPos=Vector3r(0.5,-2.5,2);
> > relPos.push_back(Vector3r(0,0,0)); radii.push_back(.5);
> > relPos.push_back(Vector3r(.5,0,0)); radii.push_back(.5);
> > relPos.push_back(Vector3r(0,.5,0)); radii.push_back(.5);
> > relPos.push_back(Vector3r(0,0,.5)); radii.push_back(.5);
> > relPos.clear(); radii.clear();
> >
> > setDefault("param_damping",.8); //(made changes in shop)
> >
> > I set up time step=10e-5 on control panel.
> >
> > thank you very much!
>
>
> _______________________________________________