Droplet deformation under pulsatile electric fields

Abstract

Highlights  Drop deformation dynamics under pulsatile electric fields is analysed.  A good quantitative agreement with experimental data is obtained.  The effects of electrical and physical parameters are quantified.  Results are compared with a linear model of the same process.  The ratio of Weber number and Ohnesorge number describes droplet deformation well.

Electrocoalescence of water droplets in sunflower oil using a novel electrode geometry

“…It is remarkable that the optimal frequency of 100 Hz obtained in the current case (see shows decreasing coalescence efficiency at high frequencies. Interestingly, it can also be seen from this figure that the frequency range 60-200 Hz, where the pulsatile electric fields perform better than the constant fields, is the same as that where a non-linear relationship of the deformation ratio versus the ratio of Weber Number and Ohnesorge Number is observed [20]. Another noteworthy point is that the sawtooth waveform has proved to perform best at the high conductivity of 3 g L -1 and low residence times (2 and 3s) among the pulsatile fields.…”

“…Notwithstanding a number of research works [14][15][16][17][18][19] conducted on the effect of the electric waveform on electrocoalescence, the understanding of the influence of the waveforms is still limited, with some contrasting conclusions. Lundgaard et al [16] and Lesaint et al [17] ranked the efficiency of AC waveforms as square > sinusoidal > triangular, which is similar to the results obtained by Li et al [20]; whereas Mousavi et al [15] reported that the coalescence efficiency of pulsed DC triangular and halfsinusoidal waves was superior to that obtained with square waves. Flat electrodes were used in the work of Lundgaard et al [16] and Mousavi et al [15], while cylindrical electrodes were used in the work of Lesaint et al [17].…”

“…The efficiency shows a maximum value at an intermediate frequency of 100 Hz for all the waveforms. The dependence of the efficiency on frequency could be interpreted considering that the oscillation of droplets and collision rate of neighbouring droplets are enhanced with increasing frequencies, in so far as the droplets can mechanically respond to the electric field, thus enhancing the coalescence.At the optimum frequency (f =100 Hz), the droplets oscillation and deformation extent are maximal as recently analysed by Li et al[20]. At higher frequencies (f >100 Hz), both the deformation extent and oscillation amplitude of droplets decrease significantly with increasing frequencies, accounting for a reduction in the coalescence efficiency.The efficiency of the constant field at the optimum intensity (200 V mm -1 ) is given in dotted line for comparison inFig.…”

“…decreases to 0 exponentially outside and inside the droplet, respectively. We follow the approach of Li et al [20] and Vivacqua et al [36], coupling Eq. 3with the Navier Stokes equations for the flow and Laplace equations for the electric field.…”

A Self‐Powered and Efficient Triboelectric Dehydrator for Separating Water‐in‐Oil Emulsions with Ultrahigh Moisture Content

“…[11][12][13] Electric dehydration has the advantages of high dehydration efficiency and quality, but it can only work at low moisture content with a complex power supply. [14][15][16] Overall, a large amount of energy or chemicals is consumed during oil-water treatment. Therefore, it is highly desired to develop a sustainable and efficient method for separating oil-water emulsions.A triboelectric nanogenerator (TENG) can instantly convert environmental energy into electricity and then serves as an energy harvester, active sensor portable power sources, and self-powered systems.…”