> ________________________ > Cundall way (as you rightly pointed out) is the following: > > *** update of velocities (he does not, but as you already said this would > be the solution): > vel+=velGrad*vel*dt > *** update of positions: > pos+=(velGrad*vel*dt)*dt > ________________________ > Currently in Yade (NewtonIntegrator): > > *** update of velocities: > vel+=(velGrad-prevVelGrad)*pos > *** update of positions: > pos+=(velGrad-prevVelGrad)*pos*dt > ________________________ > There is a term of difference between these two formulations. Basically, it > is like writing: > pos_Yade = pos_Cundall - prevVelGrad*pos*dt > > Hello Bruno,
thanks for the update in the periodic. I was thinking again about the two formulations. To the end of update positions, Cundall uses the gradient of velocity which has the same unit of measure as the strain rate. That said, why would you use (velGrad-prevVelGrad) instead of velGrad? Which is the unit of measure of the rate of the gradient of velocity? Is this formulation consistent? Taking the rate of velGrad instead of velGrad is not really the same. One more question. Why do not we move the spheres through the periodic boundaries instead of updating their positions? Would this be possible? I mean, like treating the periodic boundaries as walls. ATM, we use the rule of continuum mechanics to updated positions of discrete particles, but is this correct dealing with a particulate system? Would not be better to apply the strain rate to the moving periodic boundaries and as a consequence moving the balls? Thanks a lot for your answers. Chiara
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