Effects of surface friction on a two-dimensional granular system: numerical model of a granular collider experiment

We present numerical results from a simulation of a granular collider experiment [B. Painter, M. Dutt, and R. P. Behringer, Physica D 175, 43 (2003)] using a numerical model which accounts for substrate frictional effects [M. Dutt and R. P. Behringer, Phys. Rev. E 70, 061304 (2004)]. We find the gradual birth and growth of a central cluster for the final state of the particles that depends on the system size, the substrate frictional dissipation, and the initial average kinetic energy. For systems where a central cluster is observed in the final state, the autocorrelation function C(r) of the interparticle spacing satisfies a Gaussian functional form C(r)=Ae-(r/sigma)2. We also find that the fluctuation speed distributions adhere to a Maxwell-Boltzmann distribution for times in the vicinity of collapse. Our results strongly indicate that the principal mechanism responsible for the energy and momentum dissipation is the particle-substrate kinetic friction. Our findings reiterate the importance of considering the effects of substrate friction in particle-substrate systems, as shown by the agreement between our numerical results with experimental findings of Painter, Dutt, and Behringer.