THE RAYLEIGH APPROACH TO THE RHEOLOGY OF COMPRESSIBLE GRANULAR FLOW

We develop a Rayleigh-type approach to the analysis of compressible gr anular flow. In this approach, a (possibly negative) influx of energy from the walls is taken into account. This is greatly advantageous in granular flow rheology, since such influx of energy arises spontaneous ly as soon as the balance between the energy influx (due to whatever m echanism keeps the unperturbed system in a thermalized state) and the dissipation rate is violated. We show that standing waves, although wa ves of a rather peculiar type, may well exist, and that such waves hav e thicknesses of several hundreds particle diameters. We also give an analysis of the stability of compressible granular flow, which exhibit s some peculiar characteristics. (C) 1997 The Society of Rheology.