Gas–solid flow in a diffuser: Effect of inter-particle and particle–wall collisions

This article investigates the role of the specularity coefficient (φ, the extent of the energy dissipation due to particle–wall collisions), inter-particle restitution coefficient (e_pp, the extent of the energy dissipation due to inter-particle collisions), and four combinations of these variables on the hydrodynamics, and the pressure recovery of the dilute gas–solid suspension in a diffuser. The investigation applies the two-fluid modeling approach along with the kinetic theory of the granular flow. The present investigation's findings indicate that an increase in φ or a reduction in e_pp reduces the pressure recovery by weakening the reverse momentum transfer phenomenon, which is recognized as the primary means for the pressure recovery. Besides, in a gas–solid flow system, a higher φ or smaller e_pp enhances the particles’ trapping in the recirculation zone. The recirculation zone's strength and size increase as φ increases or e_pp reduces. Moreover, an increase in the wall–particle and inter-particle interactions strengthens the sidewise displacement of the particles. The effect of the wall–particle and inter-particle interactions are insignificant for extremely small solid loading.