Velocity Verlet scheme with velocity dependent force

Submitted by bastien on Tue, 06/18/2019 - 19:50

Dear LIGGGHTS users,
In LIGGGHTS for the integration of the velocity and the position we use a velocity Verlet scheme. This choice is motivated by the fact that we need to have a global conservation of the energy in our system. That’s why it is important to use a symplectic integration scheme.

My question is :
In the velocity Verlet scheme we assume that the acceleration at the end of the time step depend only on the position. But in DEM the contact force depends on the velocity, therefore the acceleration depends on velocity too. To my knowledge I had never seen some discussion on this issue.

With my first observations it seems that a velocity dependent force is problematic and could lead to a degradation of the second order of the scheme. And more problematic a loss of the symplectic characteristic of the scheme…

I would like to have more information on the integration of the contact force and more generally on velocity dependent force.

Regards
Bastien Delacroix