Volumetric displacement effects in Euler-Lagrange LES of particle-laden jet flows

Abstract

Large-eddy simulations (LES) of a particle-laden jet under a range of volume loadings are performed using a modified point-particle Euler-Lagrange (EL) approach to evaluate the effect of the volume/mass displaced by the subgrid particles on the flow. The spatio-temporal variations in the volume fraction of the carrier phase are taken into account giving rise to a zero-Mach number, variable density formulation with source terms in both momentum and continuity equations. The influence of volume loading as well as particle relaxation time on these volumetric displacement effects are investigated by performing numerical tests at different inlet volume loadings (0.047%-37.6%) and Stokes numbers (0.038-11.6). It is shown that for volume loadings above 5%, the volumetric displacement effects tend to become important. For the cases studied, these effects increase the mean and r.m.s. velocities of the carrier phase due to the continuity source term; however, they decrease further downstream due to dispersion of particles and spreading of the jet. It is observed that reducing the particle Stokes number increases the volumetric displacement effects due to their quick response time to the changes in the background flow, lower dispersion and smaller reaction forces.