AN EXPERIMENTAL STUDY ON THE DRAG EFFECT OF PRECIPITATING PARTICLES ON FLUID MOTION

An experiment is performed to simulate the drag effect of raindrops on the air motion in the atmos-phere by means of fine sand particles precipitating through a liquid fluid. The results suggest that the drag effect of the precipitating particles may cause the downward motion in the column where sand particles (or raindrops) precipitate, and produce the updraft around, thus forming a vertical vortex flow pattern around the precipitation area. This effect is also found to be propagating outward, resulting in a multi-vortex flow field. In the stratified fluid, vortexes can be observed at 2 or 3 levels. In the lower layer, the rotating direc-tion of vortexes varies periodically. In addition, the whole flow field induced by the drag effect of precipitat-ing particles is characterized by clear vacillation. The experimental results obtained in this paper can be used to explain the phenomena of multi-layer clouds and multi-belt rainfall around the severe rain.