Turbulence Effects on Droplets and Ice Crystal Surrogates in Mixed-Phase Experiments

In mixed-phase clouds, key processes governing cloud lifetime and precipitation formation depend critically on ice–ice and ice–droplet interactions, including secondary ice production, aggregation, and riming. By analyzing particle dynamics in a mixed-phase flow under the controlled conditions of a wind tunnel experiment, the influence of turbulence on ice crystal and droplet dynamics can be systematically investigated. Glitter particles were used as ice crystal analogs with an aspect ratio of approximately 21 (hexagonal shape; diameter: ≈ 450 µm; thickness: ≈ 21 µm), representative of natural ice crystals that are prone to riming. Water droplets with diameters between 10 and over 40 µm were generated using fog generators. Three-dimensional particle positions, velocities, orientations, and shape were simultaneously measured for individual particles using a novel holographic tracking velocimetry instrument, i.e. HoloTrack.We present first results on glitter–droplet and glitter–glitter interactions, as well as glitter orientation statistics across multiple turbulence intensities. Glitter orientation with respect to gravity, as well as glitter alignment as a function of the distance between particles, are analyzed. In addition, relative velocity statistics between glitters, and between glitters and droplets, are also investigated. This provides novel insights into the dynamics of ice–ice collisions and riming under varying turbulence conditions.