Electrostatic charging and deflection of nonconventional droplet streams formed from capillary stream breakup

Droplet streams generated from capillary stream breakup and forced with amp litude-modulated (a-m) disturbances will undergo a systematic interdroplet merging process due to their relative velocities that result from the a-m d isturbance. This paper concerns the electrostatic charging of droplets gene rated with a-m disturbances, and seeks an understanding between the competi tive effects of the electrostatic repulsive force and the momentum associat ed with relative velocities that are due to the a-m disturbance. To this en d, experimental results and numerical simulations that are in excellent agr eement and predict the configuration of the charged droplet stream are pres ented. In this work, droplets are generated with the aforementioned techniq ue and are electrostatically charged. It has been found that for droplets g enerated with a disturbance with a high degree of modulation, m, the moment um of the droplets dominates over the electrostatic force causing the dropl et merging process to be similar to the uncharged case as attested by both experimental results and numerical simulations. Here, m is the ratio of mod ulation to original carrier amplitudes. For droplets with lower values of m , the electrostatic forces dominate and it is found that the relative posit ions of the droplets will oscillate along the direction of their flight pat h with maximum excursions not exceeding one wavelength of the carrier distu rbance (i.e., the separation of the unmerged droplets). (C) 2000 American I nstitute of Physics. [S1070-6631(00)00709-1].