Instability of granular flow on rough inclined plane

yWe examine the stability of granular flow on an inclined plane in the collisional flow regime by numerical simulations. The model we use is the two dimensional disks rolling down a rough slope. We investigate the density dependence of the flowing behavior in low density region, and demonstrate that steady collisional flow appears out of accelerated behavior above a certain density of particle. It is found that, for relatively low density, the uniform collisional flow become unstable against forming a cluster.