Mechanical energy transfer for two particles in a vertically vibrating channel

We present an experiment and simulation study of two colliding particles in a vertically shaken channel driven sinusoidally. The two identical Delrin particles both have a diameter of d=5.0 mm. Multiple cases are considered for driving frequencies, f, ranging from 23 to 32 Hz and the acceleration magnitudes, Γ, from 1.78 to 3.53 g. The coefficient of restitution is observed to depend on the impact velocity strongly in both experiment and simulation. Super-elastic collisions, where the coefficient of restitution is measured to be exceeding unity, are also observed in this experiment. We examined the relative velocity and the total mechanical energy of the two particles before and after collisions in both the lab frame and the center of mass frame. Both experimental and simulation results in the lab and center of mass frame suggest the super-elastic collisions result from an occasional mechanical energy transfer between the rotational and translational degrees of freedom.