Exploring the parametric dependence of particle settling and preferential sweeping in two-way coupled turbulent flows*

In Tom & Bragg (2019), we investigated the role of different scales of turbulence affecting the settling of inertial particles, advancing the idea of the preferential sweeping mechanism (Maxey 1987), which only applied to weakly inertial particles. Building upon this theory, in Tom, Carbone & Bragg (2022), we studied how the multiscale preferential sweeping mechanism enhances the settling velocities of two-way coupled particles in the dilute particle mass loading regime. We confirmed Monchaux's (2017) observation that even in this regime, two-way coupling can significantly enhance particle settling, even though the global fluid statistics are almost unaffected. However, in contrast to Monchaux (2017), we found that preferential sweeping still plays a crucial role in the settling enhancement in the limited parameter regime considered. Here we perform direct numerical simulation (DNS) to study the problem over a much larger portion of the parameter regime. We aim to understand how the conclusions of Tom, Carbone & Bragg (2022) change if the Froude number and mass loading are varied over a much wider range than were considered in that study.