yade-users team mailing list archive

[Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx>]

> Thanks for replying again. Yes, my question was: is it right to derive 
> the branch vector from the position vector of the contact point rather 
> than getting it from the radius*normal?
Lets say it is common and not that bad, but not perfect.
> -- I remember that you tested the code and said that you were 
> comparing the results with the ones obtained from rigid boundaries 
> conditions. Have you done those tests avoiding ratcheting?
Yes.
> -- I looked again at the way we compute the relative velocity at 
> contact. I do not see anything wrong in the way we apply the shift due 
> to the change in the velocity gradient. The explosion of the sample 
> happens only for the case with ratcheting, though. It is strange, I 
> agree, but we should find an explanation. Only one doubt for the 
> moment: we update relative velocity at contact and then we also update 
> the velocities in the NewtonIntegrator class. Is this correct? I know 
> it is an old question but I still have the feeling that we are 
> updating the velocities twice (I recall that Cundall is only updating 
> particle positions and then relative velocities).
The shift in relative velocity is not updating the particle velocity, it 
is only considering the velocity of its duplicate in a different period. 
So, we are not doing something twice : velocity is updated only in 
Newton. Still, a mistake in this shift could explain explosions in some 
cases.

Cheers.

Bruno


--
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Bruno Chareyre
Associate Professor
ENSE³ - Grenoble INP
Lab. 3SR
BP 53 - 38041, Grenoble cedex 9 - France
Tél : +33 4 56 52 86 21
Fax : +33 4 76 82 70 43
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