The dynamics of thin disks falling in quiescent air

Laboratory experiments are performed with 1, 2, and 3mm diameter thin disks falling in a large quiescent air chamber, with results relevant to plate ice crystals in the atmosphere. Virtually all previous studies concerned with disk falling dynamics used larger analogue particles in liquid fluids, thus focusing on the behavior of singular particles at relatively small density ratios. In our experiment, we aimed to match the conditions typical of atmospheric precipitation more closely by releasing a controlled volume fraction of realistically sized disks with a high density ratio in air. Through high-speed 2D Particle Tracking Velocimetry (PTV), we obtain the planar disk trajectories as well as the necessary information to reconstruct their full 3D angular motion. This presentation will focus on results related to the individual disk dynamics – including their rotation rates, falling styles, and distinct behaviors based on the disk diameters and the fall style of each trajectory. Torque scaling and particle response times, both translational and rotational, will also be considered.