An Improved Multiscale Model for Dilute Turbulent Gas-Particle Flows Based on the Equilibration of Energy Concept

The objective of this study is to assess, and possibly improve, models for turbulent particle-laden flows. We begin by understanding the behavior of two existing models—one proposed by Simonin [Von Karman Institute of Fluid Dynamics Lecture Series, 1996], and the other by Ahmadi [Int. J. Multiphase Flow, 1990]—in the limiting case of statistically homogeneous particle-laden turbulent flow. The decay of particle and fluid phase turbulent kinetic energy (TKE) are compared with direct numerical simulation results. Even this simple flow poses a significant challenge to current models which have difficulties in reproducing important physical phenomena, such as the variation of TKE decay with particle Stokes number. Some of these problems can be traced to the model for the interphase TKE transfer timescale. A new model for the interphase transfer timescale is proposed that accounts for the interaction of particles with a range of fluid turbulence scales. A new multiphase turbulence model—the Equilibration of Energy Model (EEM)—is proposed, that incorporates this multiscale interphase transfer concept. The particle and fluid TKE evolution predicted by this new EEM model correctly reproduce the trends with particle Stokes number.