title: Gravity-driven enhancement of heavy particle clustering in turbulent flow.
abstract: Heavy particles suspended in a turbulent flow settle faster than in a still fluid. This effect stems from a preferential sampling of the regions where the fluid flows downward and is quantified here as a function of the level of turbulence, of particle inertia, and of the ratio between gravity and turbulent accelerations. By using analytical methods and detailed, state-of-the-art numerical simulations, settling is shown to induce an effective horizontal two-dimensional dynamics that increases clustering and reduce relative velocities between particles. These two competing effects can either increase or decrease the geometrical collision rates between same-size particles and are crucial for realistic modeling of coalescing particles.
authors.affiliation: Laboratoire Lagrange, Université de Nice-Sophia Antipolis, CNRS, OCA, Boulevard de l'Observatoire, 06300 Nice, France.
authors.forename: Jérémie
authors.initials: J
authors.lastname: Bec
authors.affiliation: Laboratoire Lagrange, Université de Nice-Sophia Antipolis, CNRS, OCA, Boulevard de l'Observatoire, 06300 Nice, France.
authors.forename: Holger
authors.initials: H
authors.lastname: Homann
authors.affiliation: International Centre for Theoretical Sciences, Tata Institute of Fundamental Research, Bangalore 560012, India.
authors.forename: Samriddhi Sankar
authors.initials: SS
authors.lastname: Ray