> De : Vincent Richefeu <[email protected]> > Date : 9 décembre 2009 09:35:42 HNEC > À : boon chiaweng <[email protected]> > Objet : Rép : [Yade-users] Questions on equations (contact laws, velocity, > libraries) > > > Le 9 déc. 2009 à 03:06, boon chiaweng a écrit : > >> Q3. The position/velocity integration follows the 2nd order explicit >> method, as was upgraded by Bruno :). The velocity and angular velocity are >> in the (t+dt/2) timestep, while the position & acceleration (also rotation) >> are in the (t) time step. But it is not adjusted back to the current time >> step: v(t) = v(t-dt/2) + v(t+dt/2). Ommitting this will make the >> velocities in the simulation ahead of time by dt/2? Is this alright? Why? > > Hi boon, > > I cannot answer all your questions, but only give an opinion for Q3. > I think you're right. This may be critical point only for "viscous" damping. > I think that something like the Beeman's algorithm should be a better > candidate than leap-frog or velocity Verlet when viscous damping (with high > velocities) is "activated". With quasistatic simulations, it seems not to be > critical since viscous damping is a kind of "regularizator". With Cundall > Damping, no problem since velocities are not required if the force-laws. > > Vincent > >
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