Droplet Deformation under Conditions of Neutral Buoyancy

One of the classical problems of hydrodynamics is the problem of droplet deformation in the state of neutral buoyancy under the action of an external force. It is assumed that if the droplet size is initially equal to or less than the capillary diameter, it takes the shape of a regular sphere, regardless of the density gradient in the environment and the droplet, the degree of their mutual solubility, the possibility of Marangoni convection, and the time elapsed since the creation of the system of liquids. To elucidate the influence of these unaccounted factors as well as that of initial deformation of the droplet, we experimentally studied the evolution of the shape of large-diameter droplets in the solution with density stratification. The droplet behaviour was studied in the case when it took the form of a spheroid flattened vertically under the action of gravity. The interferometer was used to visualize the distribution of solution concentration near the drop. The dependence of the ratio of the vertical to horizontal diameter of the droplet on time and the average concentration gradient in the surrounding medium was determined. (paper)