Energy loss at propagating jamming fronts in granular gas clusters

We explore the initial moments of impact between two dense granular clusters in a two-dimensional geometry. The particles are composed of solid CO(2) and are levitated on a hot surface. Upon collision, the propagation of a dynamic "jamming front" produces a distinct regime for energy dissipation in a granular gas in which the translational kinetic energy decreases by over 90%. Experiments and associated simulations show that the initial loss of kinetic energy obeys a power law in time ΔE = -Kt(3/2), a form that can be predicted from kinetic arguments.