There are many experimental observations reported in literature of suspension flows of particles which include fines clouds in gases or neutrally-buoyant particles in liquids (Hanes and Inman, 1985; Bagnold, 1954) where the common phenomenological feature is the inertial agitation of the particle assembly as a function of the granular temperature. The interstitial drag imposed by the gas, as well as the surface attractive forces between the particles, both play a part in presenting a resistance to agitation. In this paper, we develop an analysis based on the premise of 'highly thermalised' particulate systems as previously described by the kinetic theory approach. We consider the hydrodynamic drag as a function of the fluctuating component of the particle velocities which results in a 'velocity of approach' dependent percolation resistance for the interstitial movement of the gas between the particles. The short-range surface forces are assumed to act only when particle surfaces touch during collisions. We arrive at a measure of total resistance force components of interfacial phenomena. The early results indicate a strong dependence of the total dynamic resistance to agitation on the ratio of the two time constants describing assembly relaxation and individual particle collisions. The analysis is predominantly concerned with the fluctuating velocity fields, and hence the effect of gravity, which scales the mean flow field, is not addressed directly.
|Title of host publication||Proceedings of the 1999 3rd ASME/JSME Joint Fluids Engineering Conference, FEDSM'99, San Francisco, California, USA, 18-23 July 1999|
|Publication status||Published - 1999|