A wind tunnel investigation of the deformation of water drops in the vertical and horizontal electric fields

Abstract

Deformation of the uncharged water drops freely suspended in a vertical wind tunnel and subjected to vertical, horizontal, or no external electric field is investigated using movie photography. Electric field elongates the drop along its direction, and the elongation increases with the increase in electric field. Horizontal electric fields are more efficient than vertical ones in deforming the drop. The larger the drop, the larger is the difference between the distortions in the vertical and horizontal field configurations. As compared to the case of no electric field, horizontal electric field, as low as 1 kV cm^-1, changes the ratio of minor-to-major axis of the 2.6-mm diameter drop by ~3%. An examination of the frequency distribution of the drop's axis ratio shows that during its oscillations, oblateness decreases more often when subjected to vertical electric field and increases more often when subjected to horizontal electric field. Extreme values of distortion increase and are attained more frequently when drop is oscillating in electric field. It is concluded that the drop size distribution will be wider and thus the rate of drop's growth faster in those regions of cloud where the electric field direction is vertical rather than horizontal.