Generating the granular solitary wave

Based on the generalised Saint-Venant equations for granular flow on an inclined chute, we show how to generate solitary waves from localised perturbations at the inlet. Such perturbations usually give rise to a group of roll waves, but by choosing the system parameters appropriately, the formation of all but the first wave can be suppressed, thus turning this first one into a solitary wave. This calls for a highly diffusive flow, which is realised for inclination angles close to the minimal angle required to keep the granular material flowing.