Drop Size Distribution

The flow of oil-in-water emulsions through quartz micro-capillary tubes was analyzed experimentally. The capillaries were used as models of connecting pore-throats between adjacent pore body pairs in high-permeability media. Pressure drop between the inlet and outlet ends of the capillary was recorded as a function of time, for several values of the volumetric flow rate. Several distinct emulsions were prepared using synthetic oils in deionized water, stabilized by a surfactant (Triton X-100). Two oils of different viscosity values were used to prepare the emulsions, while two distinct drop size distributions were obtained by varying the mixing procedure. The average oil drop size varied from smaller to larger than the neck radius. The results are presented in terms of the extra-pressure drop due to the presence of the dispersed phase, i.e. the difference between the measured pressure drop and the one necessary to drive the continuous phase alone at the same flow rate. For emulsions...

Increasing our understanding of the small scale variability of drop size distributions (DSD), and therefore of several bulk characteristics of rainfall processes, has major implications for our interpretation of the remote sensing based estimates of precipitation and its uncertainty. During the spring and summer of 2002 the authors conducted the DEVEX experiment (disdrometer evaluation experiment) to compare measurements of natural

The aim of this work is to compare the oil-in-water emulsions produced by mechanical agitation (Ultra-Turrax, 10000rpm, P=170W) or power ultrasound (ultrasound horn, 20kHz, 130W) using the same model system : water/kerosene/polyethoxylated (20EO) sorbitan monostearate. The following parameters were varied : emulsification time, surfactant concentration, consumed power and volume fraction of oil. With ultrasound, the drop size (Sauter diameter, d32)

The extent to which dispersed-phase viscosity influences equilibrium mean drop size and drop size distribution at constant interfacial tension is determined for dilute suspensions by dispersing silicone oils of various viscosity grades in water. A mechanistic model for mean drop size is developed which predicts the moderate-viscosity data and whose parameters correlate the high-viscosity results. Trends in the mean size data coincide with those for the drop size distribution, which broadens considerably as viscosity increases and suggests a dependency on breakage mechanism.

Liquid-liquid mixing is a key process in industries that is commonly accomplished in mechanical agitation systems. Liquid-liquid mixing performance in a stirred tank can be evaluated by various parameters, namely minimum agitation speed, mixing time, circulation time, power consumption, drop size distribution, breakup and coalescence, interfacial area, and phase inversion. The importance of these liquid-liquid mixing parameters, the measurement method, and the results are discussed briefly. Input parameters such as impeller type, power number, flow pattern, number of impellers, and dispersed phase volume fraction, in addition to physical properties of phases such as viscosity and density, are reviewed. Scale-up aspects are also included. © 2013 Copyright Taylor and Francis Group, LLC.

http://www.tandfonline.com/doi/pdf/10.1080/00986445.2012.717313

Optical disdrometers have the potential to be low maintenance instruments that can measure drop-size distributions and drop-size distribution moments such as rainfall rate, radar reflectivity, optical extinction, and others. As with any other measurement device, their output is affected by different sources of uncertainty. To better understand these uncertainties, we compared rainfall accumulations that were measured by three dual tipping bucket stations, three Vaisala WXT510 compact weather stations, and four Thies optical disdrometers. We detected considerable bias between disdrometers and tipping buckets, as well as among disdrometers, that we attempted to minimize through calibrating diameter measurements. Although the calibration successfully decreased bias among disdrometers, it increased bias between disdrometer rainfall accumulations and tipping bucket accumulations, indicating that there are other relevant sources of error in the estimation of rainfall accumulation from disdrometer measurements. We developed a simulation capable of mimicking the disdrometer's operation during the calibration procedure and studied the effects of using three arbitrary laser beam patterns into the measurement of the spheres' diameters. The simulation successfully reproduced some of the behavior observed in calibration data, showing the dependence of the bias and the spread of sphere diameter measurements on the studied beam patterns. Furthermore, we designed a Monte-Carlo-based simulation to propagate the uncertainties of the measurement of spheres' diameters into the estimation of rainfall accumulations. We used the calculated uncertainties to correct rainfall accumulations which improved the agreement among disdrometers, although apparently overcorrected the accumulation for one of the instruments. Moreover we found the average correction to be related to both average and standard deviation of the diameter error and insensitive to the diameter error skewness. Overall we observed considerable bias between instruments with different principles of measurements, which could not be solely explained by uncertainty in the evaluation of the diameters, or by wind effects, indicating that difficulties in the determination of the optical disdrometer's sensing area could be the cause.► We detected bias between disdrometers and rain gauges, as well as among disdrometers. ► Detected bias could only be partially addressed by calibrating diameter measurements. ► We discarded wind effects as causes for the observed errors. ► The presented simulation framework allows the assessment of optical induced errors.

Disdrometer data measured during the passage of tropical continental squall lines in Darwin, Australia, are analyzed to study characteristics of raindrop size distribution (DSD). Fifteen continental squall lines were selected for the DSD analysis. An observed squall line was partitioned into three regions based on radar reflectivity pattern, namely, convective line, stratiform, and reflectivity trough. A convective line was further

The depolarization of a satellite signal due to scattering by rain drops has been studied at a tropical location.
The depolarization phenomenon is observed in terms of an enhancement of cross-polar component of a horizontally
polarized Ku-band signal. The differential phase shifts, dominantly responsible for causing depolarization at Kuband
due to scattering by spheroidal raindrops, are computed by employing the point matching technique and using
experimentally obtained rain drop size distribution (DSD) data. The differential phase shift is significant for large
drops (> 3mm). Consequently, DSD plays an important role in determining the depolarization of the satellite signal.

Vertically pointing Micro Rain Radars (MRRs) provide profiles of drop size distributions (DSDs) from the measured Doppler reflectivity spectra. However, in the presence of strong vertical winds, the measured spectra can suffer from aliasing errors. These errors can considerably affect the derived DSD, and hence, the retrieved rain parameters. In this work, we show that such aliasing can be automatically detected and that this detection can be used at our benefit to identify strong vertical winds and eliminate incorrect retrievals. Likewise, we show that when this aliasing is adequately corrected, the retrieved DSD is then fit for further parameter retrievals.