A hyperbolic model for fluid–solids two-phase flow

A long unresolved problem in two-phase flow is that the inviscid form of a standard model is not hyperbolic, making initial-value problems based on the model ill-posed. In this paper we show that the model becomes hyperbolic when the buoyant force term in the model is modified to include the effect of relative motion between the phases. We also show that the new model gives physically realistic solutions for minimum fluidization, expansion of a tapered fluidized bed, and the flow of a neutrally buoyant mixture through a nozzle and compare the solutions with those of the standard model and an alternative model.