Turbulence and its Effect on Droplet Collisions in Multiphase Fluid Flows
Understanding the dynamics of particles in turbulent flows is important to many engineering and environmental problems including spray atomization, and cloud droplet growth and precipitation. We are studying the effect of turbulence on droplet collision-coalescence in an effort to clarify its role in the process of warm rain formation. Our research will help test the hypothesis that turbulence-induced collisions can explain the size gap between the limit of condensational growth and the onset of gravitational sedimentation. We use wind tunnel experiments to study the evolution of water droplets in homogeneous, isotropic, grid turbulence. Small water droplets are injected into the wind tunnel and their diameter, position and velocity are measured using both Phase Doppler Particle Analysis (PDPA) and Particle Image Velocimetry (PIV). Also, we are using high-speed visualizations of the droplet dynamics to understand and quantify droplet coalescence efficiency.