Hydrodynamics of polydisperse gas-solid flows: Kinetic theory and multifluid simulation

Polydisperse gas -solid flows, which is notoriously difficult to model due to the complex gas -particle and particleparticle interactions, are widely encountered in industry. In this article, a refined kinetic theory for polydisperse flow is developed, which features single -parameter Chapman-Enskog expansion (the Knudsen number) and exact calculation of the integrations related to pair distribution function of particle velocity without any mathematical approximations. The Navier-Stokes order constitutive relations for multifluid modeling of polydisperse gas -solid flow are then obtained analytically, including the solid stress tensor, the solid -solid drag force, the granular heat flux and the energy dissipation rate. Finally, the model is preliminarily validated by comparing to the discrete element simulation data of one-dimensional granular shear flow and by showing that the hydrodynamic characteristics of gas -solid flows in a bubbling fluidized bed containing bidisperse particles can be successfully predicted.