Settling of inertial nonspherical particles in wavy flow

Abstract

Motivated by the problem of microplastics in the ocean, we experimentally investigate settling of plastic rods, disks, and spheres in wavy flows. We find that particle average vertical velocity can both increase and decrease in waves, relative to particle settling velocity in quiescent flow. This variation is a function of flow inertia at the particle length scale, characterized by particle Reynolds number Re${}_{p}$, and also of particle shape. We find that even though the relative vertical velocities between particles and flow remain constant with Re${}_{p}$, the particles nonuniformly sample the flow as a function of particle shape and Re${}_{p}$.