Influence of preferential concentration on the settling of heavy particles in homogeneous turbulence

We analyze one-way and two-way coupling Direct Numerical Simulation (DNS) data of heavy particles settling in homogeneous turbulence. An extended range of particle Stokes numbers (St), Rouse numbers (R) and mass loading is considered. Influence of preferential concentration on the settling velocity enhancement is addressed from statistics of particle and flow field quantities conditioned on the local concentration by making use of Voronoï diagrams. Gravity is found to have almost no influence on the global characteristics of preferential concentration, while the conditional statistics evidence a refined preferential sampling of the flow field resulting from the gravitational effects. A 2D analysis of the Voronoï cells is also presented to investigate their shape and orientation with respect to gravity direction.