Abstract
The time-averaged axis ratios, frequency and amplitude of oscillations of water drops of 2.67–6.6mm diameter were determined by suspending them in a vertical wind tunnel in the absence and presence of horizontal electric fields using a high speed camera at 1000 frames per second. A systematic decrease in the drop's axis-ratio is observed with increase in its diameter and/or horizontal electric field. The results revealed with high speed photography are in good agreement with earlier results. The drop distortion due to horizontal electric field is more pronounced for the drops in the size-range of 3.36–6mm diameter showing that the electrical forces progressively enhance the horizontal elongation of the drop resulting in its instability at 6.6mm. The drop oscillation frequency computed from temporal variation of axis ratio, decreases with increase in drop size but shows no significant change in oscillation frequency in the horizontal electric field of ≤500kVm−1. However, the oscillation amplitude increases with increase in drop size up to a threshold value and then flatten-off in the electric field of ≤300kVm−1 demonstrating the nonlinear effect of net forces acting on such large drops. In higher electric field of 500kVm–1, gradual increase in the amplitude of oscillation with an increase in drop diameter has been observed. Moreover, for a particular drop size, the amplitude of oscillation decreases with increase in the electric field upto 500kVm−1. The oscillation frequency of the waterdrops experiences multimode oscillations. The dominant fundamental mode of oscillations (2,0) always exists for all drops in our experiments along with the coexistence of higher modes of oscillations i.e. (2,1) and (2,2) mode. Possible effects of electrical forces on shape parameters and their implications on cloud microphysics and in radar meteorology are discussed.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call