Experimental investigation on single drop breakage in two-stream impinging microchannels

Abstract

Experimental study on drop breakage is carried out in the microchannels utilizing head-on impingement configuration by observing single drop breakup process. In this study, the breakage of oil drops with diameter ranging from 30 to 200 μm is investigated in the vicinity of flows impingement region by using high-speed photography at varied flow rate conditions. The most prominent phenomenon of the single drop breakup in the two streams impinging flow field is that the drop tends to break into multiple fragments. The breakage time and the number of daughter drops in the resulting population are statistically analysed and found to be highly dependent on the mother drop size and energy dissipation rate. Two different micro-system geometries, the 600-600 system and the 600-300 system, are compared to evaluate the advantages and disadvantages of swirl flow developed due to the off-axis layout of inlet channels in the 600-300 system. The results show that swirl flow establishes a low pressure area acting as the dead zone, where drop can be trapped and then drastically stretched to breakup. Compared with the 600-600 system, the detrimental effect of swirl flow inside the 600-300 system on increasing the breakage time can be offset by much greater amount of daughter drops generated. In general, the 600-300 system performs more effectively than the 600-600 system because of the less isotropic flow feature. And this superiority is more distinct when energy dissipation rate is higher. Acronyms Ca Capillary number,-DDSD daughter drop size distribution,-Re Reynolds number,-SSI swirl strength index,-We Weber number,-Wet Weber number in turbulent flow,-We* Weber number defined in this study,

Effect of cross-slot configuration in microfluidics on o/w emulsification at high throughput

“…7 at 𝑅𝑅𝑅𝑅 𝑐𝑐 of 1524, with the oil fraction of 10%. The probability distribution agrees well with the lognormal distribution; this is consistent with the fact that the dispersed phase undergoes statistically mostly several successive events of break-up (Ji et al 2021). It indicates that the symmetric configuration shows strength in generating finer dispersions than the asymmetric one.…”

Dynamics of a Newtonian droplet in the turbulent flow of a shear thinning fluid in a microchannel

“…The flow rates of the discharged fluids are found to be equal (within 1%). The mean velocity at the outlets U O is obtained by measuring the outlet flow rates ṁo1 = ṁo2 = ṁo , [2,16].…”

“…The bulk Reynolds number is defined by Re = ρUi2H2 ηx . The viscosities of the xanthan solutions are obtained by interpolation of the rheological flow curves corresponding to the mean shear rates estimated using the flow rates, γ = 2Qi2 As already stated through the paper, such flows have been previously employed for producing emulsions at high throughput, [15,16].…”

“…Liquid-liquid dispersion and the background flow in the microfluidic device were experimentally investigated in a broad range of flow rates, [15,16]. Through these experiments the Reynolds number (estimated for the continuous aqueous phase, not by using the droplet size) was varied from 1000 to 7000 and the oil dispersed volume fraction varied between 3% and 30%.…”

Analysis of droplet displacement during transport of polydisperse emulsion as drug carriers in microchannels

“…The flow patterns in cross-slot microsystems employing head-on impingement of oil and water jets for emulsifying were studied (Ji et al 2020). Droplet size measurement at different flow conditions was carried out to analyze benefits or detriments of the presence of a swirl flow and its role for the drop breakage in microsystems (Ji et. al.…”