Water droplet deformation in gas stream: Impact of temperature difference between liquid and gas

Experimental investigations were conducted to study the macroscopic behaviors of water droplets (diameter from 3 mm to 6 mm and velocities from 0.5 m/s to 5 m/s) deformed during falling down in a gas stream. Various temperatures of gases (275-1100 K) and water droplets (275-360 K) were considered. The investigations were conducted by using optical cross-correlation technics to measure the displacement velocity of droplets and the liquid convection as a function of time. High-speed (105 frames per second) video camera allowed to record the shape deformations. Two deformation modes were identified. The relationships between the shapes of droplets, their velocities and sizes were established. The impact of the temperature difference across the liquid-gas interface on the deformations characteristics was accurately analyzed. The main deformation properties (amplitude, length and period of one shape oscillation cycle) were evaluated at different temperatures of the surrounding gas and of the droplets; the velocities and sizes of droplets were measured and correlated with the shapes of droplets and their periods of oscillation.