Internal wave - granular temperature interaction: an energy balance study on granular flow

Recent work demonstrated that under a certain resonance condition a granula r flow becomes unstable to internal wave oscillations. The generated oscill ation may result in an optimization of the flow by reducing the net power l oss to frictional drag. The present paper examines possible interaction bet ween ordered oscillations and granular temperature within a high-speed gran ular flow. It will be shown that one consequence of the initial generation of the internal waves is that there will be a net reduction in the granular temperature. In effect, the instability amounts to a conversion from chaot ic to ordered oscillation, and thus a more efficient transport. The subsequ ent evolution of the now, beyond the initial instability phase will be inve stigated in this study. The primary flow is assumed to consist of a sliding layer of negligible granular temperature placed above a high-shear basal l ayer of significant granular temperature. Each layer may grow or decrease i n depth as the flow develops downstream and the two layers exchange mass ac ross the interface. A now instability behaving as a landslide with mixing c onfined to a thin layer near its base may evolve with time to become a full y-mixed debris flow, or vice-versa.