Effect of Stefan flow on the drag force in flow past random arrays of spheres

Abstract

Stefan flow is a mass flow perpendicular to the particle surface induced by the reaction or component diffusion occurring inside particles. It significantly affects the interphase transfer process in gas–solid reacting flows. In this work, a second-order immersed boundary-lattice Boltzmann method (IB-LBM) is adopted for analyzing the influence of Stefan flow on the drag force in flows past fixed random arrays of spherical particles. The effect of Stefan flow is introduced by assigning specific fluid velocities at Lagrangian markers on the sphere surface. The simulation results show that the drag force exerting on particles decreases as the Stefan Reynolds number increases. The drag force reduction caused by Stefan flow is weakened as the solid volume fraction increases. This is because the thick boundary layer caused by Stefan flow on each particle is suppressed by Stefan flow from their neighboring particles. Based on the simulation results, a novel drag correction coefficient is developed, which considers the joint influence of the Stefan Reynolds number, particle Reynolds number and solid volume fraction.