Multiphase flows laden with interacting polydisperse particles are frequently encountered in aerospace propulsion, atmospheric flows, as well as in environmental and medical applications. The stability characteristics of such flows can experience drastic changes compared to their clean state due to inter-phase and inter-particle heat and mass transfer. Disperse particulate matter has been found to alter the onset of laminar to turbulent transition and lead to modulation of turbulence in multiphase flows. Saffman (1962) conducted the first linear stability analysis of particle-laden shear flows and proposed that the addition of fine dust either stabilizes or destabilizes the carrier gas flow depending on the particles’ relaxation time scales relative to the carrier flow time scale. Numerical simulations of multiphase flows that involve tracking each interacting particle in a Lagrangian framework require extreme computational resources and are thus limited for the study of stability. The complexity of such flows is further increased when interactions such as droplet evaporation, coalescence, breakup, etc., are considered.
To extend current hydrodynamic stability theories in multiphase flows and analytically resolve interacting polydisperse particles, we revisit Saffman’s theory for dusty gas flows and develop a new generalized mathematical framework by combining a linear stability analysis and a discrete Eulerian formulation for the flow and dispersed matter. In this talk, we will introduce the generalized mathematical framework and present the stability characteristics of multiphase flows involving different shear flow configurations: Polydisperse Channel flows and Polydisperse evaporating pipe flows at low and high Reynolds numbers and various particulate matter loadings. Finally, we discuss the specific mechanisms responsible for the onset of instability in each particle-laden flow case.
