On the Phenomena of Collision-Coalescence between a Large Water Drop and Water Droplets during Free Fall at Terminal Velocity

Abstract

Preliminarily collision-coalescences between a large water drop and water droplets under free fall were observed. Movements of the droplets due to the effect of the large water drop were also observed.
The main experiment was performed by the use of a large water drop and droplets under free fall at terminal velocity, and it was proved that collision-coalescences occurred between them under the condition similar to natural rainfall. The size of the water drop and the size range of the droplets used were 6.2mm and 80 microns to 200 microns in diameter respectively.
Droplets which collided with a drop as they fell in front of the drop were all captured by the drop and no repulsion was observed between them. It was observed that smaller droplets behind a large drop were not captured by the latter because of the wake effect. Furthermore, collisions or coalescences between droplets were not observed within the large drop's wake.