Volumetric Displacement Effects of Dispersed Phase on the Euler-Lagrange Prediction of a Dense Spray (2004.05317v1)

Abstract: Accurate prediction of a dense spray using an Euler-Lagrange approach is challenging because of high volume fraction of the dispersed phase due to subgrid cluster of droplets. To accurately model dense sprays, one needs to capture this effect by taking into account the spatio-temporal changes in the volume fraction of the carrier phase due to the motion and presence of the dispersed phase. This leads to zero-Mach number, variable density equations which are commonly neglected in the standard two-way coupling spray simulations. Using pressure-based solvers, this gives rise to a source term in the pressure Poisson equation and a non-divergence free velocity field. To validate the predictive capability of such approach, an atomized non-evaporating dilute particulate round jet is first examined using Large Eddy Simulation coupled with Point-Particle approach and then higher volume loadings up to 38% are investigated with and without taking into account the volumetric displacement effects. It is shown that for volume loadings above 5%, the volumetric displacement effects enhance dynamics of the flow resulting in a higher stream-wise mean and r.m.s. velocities compared to the results of standard two-way coupling. This is more pronounced for the near field of the jet where local volume fraction of the dispersed phase is relatively high. This enhancement is conjectured to be due to the velocity divergence effect due to the modified continuity equation where spatio-temporal variations in volume fraction of the carrier phase increases velocity in the regions of high void fraction.