Disks settling in turbulence: an experimental study

The settling dynamics of plate crystal hydrometeors in nature are influenced by atmospheric turbulence. Quantifying the change in settling behavior due to the turbulence is necessary to fully understand and ultimately predict frozen hydrometeor settling under given atmospheric conditions. In this study, a large experimental air chamber is used to produce various turbulence intensities. Solid disks with comparable size and density ratio to plate crystals in the atmosphere are released into the chamber at controlled volume fractions. Through planar imaging, time‑resolved images are captured and are analyzed to obtain translational and rotational quantities of the disk motion. Results at two turbulence intensities are compared to those under quiescent conditions to examine how adding turbulence to the system affects the settling behavior. Under turbulent conditions, the non-tumbling (stable) falling style is eliminated and an increasing trend in tumbling angular velocity with increasing disk size becomes prominent at the highest turbulence intensity considered. Additional experiments with a perforated disk geometry are briefly introduced along with some initial results.