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[Giulia Macaro <question207881@xxxxxxxxxxxxxxxxxxxxx>]

New question #207881 on Yade:
https://answers.launchpad.net/yade/+question/207881

Hi,

I am running a simulation in which a constant vertical velocity is applied to a non-dynamic cylindrical body laying on a packing of spheres with periodic boundaries.
The velocity is applied through TranslationEngine(velocity=-0.01,translationAxis=[0,0,1]).
I have coded myself the cylindrical body I am working with, in a way similar to the chained cylinder.  It is still experimental, since I am still checking if it works correctly.

At some point the contact force on the cylinder becomes very high, and the spheres in contact with it start moving extremely fast (almost as if the packing is exploding). See the images:
http://www.2shared.com/photo/e7PFqYLJ/00790.html
http://www.2shared.com/photo/wY5rowcJ/00791.html
http://www.2shared.com/photo/0N4N71xE/00792.html

1.
I am wondering if anybody has faced the same issue with similar simulations.
I am not sure if this is a problem of the interaction sphere-cylinder, but it seems working fine for part of the test, and then the packing starts exploding.  I have tried to reduce the loading velocity and the time step, but it still happens.
Could it be related to the verletDist and targetInterv, maybe because the particles are moving too fast and the interaction are not detected? I am using the default values for now.

2.
Assuming that the problem might be the optimization with the verlet distance, I have few question about it.
I see that targetInterv is =50 by default, so the distance is adjusted, isn't it?
It isn't that clear the difference between the sweepLength, the verletDist and the sweepDist.  I understood what is the verletDist for, but then the other two variables seem very similar.
And also, in which range should I vary the verletDist and targetInterv? Are there any references about it?

Thanks for any suggestions
Giulia


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