Collisions between the particles and between the particles and the wall lead to deceleration of the particles and a decrease in the kinetic energy of the system.nIn the regime of small pipe to particle diameter ratios, the distribution of the flow along the pipe may be strongly affected by geometric effects as the number of possible arrangements of the particles along the cross section of the pipe affects the probability of the formation of a stable arch. the jamming probability increases with the probability that a stable arch along the cross section of the pipe is formed. nThis already done in many previous studies with different commercial software?s but not with Ansys. The problem is, to detect the collision time, the time step size must be very short within 10^-6 for a time-period of 5-10 sec. Is it possible to perform that with Ansys? I have run a simulation withen this short time step size, and it was very very slow like 3 % iteration for 24 hrs. nRegardsn