> > Hello Bruno, > I am a little bit confused about the periodic. In NewtownIntegrator we > update the velocities and _then_ we integrate the positions. This is exactly > the way of Cundall (I am checking the equations right now) except that he > chooses to update positions and not velocities (defining a strain rate > instead of a gradient of velocity which we said is fine but not in the > general case). I understand that the reason why Cundall updates the relative > velocities at contact (btw, according to his paper this is not meant to be > only for the shear direction) before going for the computation of contact > forces is that he was not updating the velocities at the level of the > integration. So my guess is: why do we need to update the relative > velocities if that has already been done in NewtonIntegrator? That would > have made sense if updating positions and not velocities. Bruno, you said > there was a problem using periodic ScGeom before the last changes. Where you > testing with homothetic=1? Because I think that case you would have needed > to update velocities (which is not a problem in Dem3dofGeom). > >> >> I have been looking at molecular dynamics (sorry for my lack of knowledge in this field) and I see that "shift2" as well as the "shift" introduced recently by Bruno for the velocities, are independent by the way we update displacements (or velocities) in NewtonIntegrator. If I have got it right, this shift has to deal with the periodicity (though I will reread carefully the part of the code where this is computed). This shift is not described in Cundall paper, that is why I got confused. Btw, why do you choose to update the cell in Scene?
cheers. Chiara > >> >> >> _______________________________________________ >> Mailing list: >> https://launchpad.net/~yade-users<https://launchpad.net/%7Eyade-users> >> Post to : [email protected] >> Unsubscribe : >> https://launchpad.net/~yade-users<https://launchpad.net/%7Eyade-users> >> More help : https://help.launchpad.net/ListHelp >> > >
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