Study of drop coalescence and mixing in microchannel using Ghost Particle Velocimetry

Kovalchuk, N. M.; Chowdhury, J.; Schofield, Zoe; Vigolo, Daniele; Simmons, Mark

doi:10.1016/j.cherd.2018.01.034

Cited by 16 publications

(27 citation statements)

References 34 publications

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“…Characterisation of flow pattern. In order to evaluate the changes in flow characteristics due to the presence of flexible valves, we used a recently developed all-optics technique, ghost particle velocimetry (GPV) [26][27][28][29][30] . GPV uses nanoparticles and bright field microscopy to generate a speckle pattern used to track the flow (see Supplementary Methods; Supplementary Figs.…”

Section: Resultsmentioning

confidence: 99%

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The role of valve stiffness in the insurgence of deep vein thrombosis

et al. 2020

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Deep vein thrombosis is a life-threatening development of blood clots in deep veins. Immobility and blood flow stagnancy are typical risk factors indicating that fluid dynamics play an important role in the initiation of venous clots. However, the roles of physical parameters of the valves and flow conditions in deep vein thrombosis initiation have not been fully understood. Here, we describe a microfluidics in vitro method that enabled us to explore the role of valve elasticity using in situ fabrication and characterisation. In our experimental model the stiffness of each valve leaflet can be controlled independently, and various flow conditions were tested. The resulting complex flow patterns were detected using ghost particle velocimetry and linked to localised thrombus formation using whole blood and an aqueous suspension of polystyrene particles. In particular, valves with leaflets of similar stiffness had clot formation on the valve tips whereas valves with leaflets of different stiffness had clot formation in the valve pocket.

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Section: Resultsmentioning

confidence: 99%

“…Ghost particle velocimetry. We tracked the flow exploiting GPV [26][27][28][29] . We used bright field microscopy and 200 nm PS particles (0.2% w/v, Sigma Aldrich, UK) as tracers.…”

Section: Methodsmentioning

confidence: 99%

The role of valve stiffness in the insurgence of deep vein thrombosis

et al. 2020

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“…The flow fields inside the dispersed phase were studied using Ghost Particle Velocimetry (GPV) (Buzzaccaro et al 2013;Kovalchuk et al 2018a;Riccomi et al 2018). This technique uses the speckle patterns produced by light scattered by particles smaller than the diffraction limit as a flow tracer.…”

Section: Methodsmentioning

confidence: 99%

Drop formation in microfluidic cross-junction: jetting to dripping to jetting transition

Kovalchuk

Sagisaka

Steponavicius

et al. 2019

Microfluid Nanofluid

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The regimes of drop generation were studied in a Dolomite microfluidic device which combined both hydrodynamic and geometrical flow focusing over a broad range of flow rates. A series of aqueous dispersed phases were used with a viscosity ratio between continuous and dispersed phases of close to unity. Surfactants were added to alter the interfacial tension. It was shown that the transition from dripping to jetting is well described by the capillary numbers of both the dispersed and continuous phases. Only the jetting regime was observed if the capillary number of the dispersed phase was above a critical value, whereas at smaller values of this parameter a jetting → dripping → jetting transition was observed by increasing the capillary number of the continuous phase. The analysis performed has shown that the conditions for a dripping to jetting transition at moderate and large values of the capillary number of the continuous phase can be predicted theoretically by comparison of the characteristic time scales for drop pinch-off and jet growth, whereas the transition at small values cannot. It is suggested that this transition is geometry mediated and is a result of the interplay of jet confinement in the focusing part and a decrease of confinement following entry into the main channel. The flow fields inside the jet of the dispersed phase were qualitatively different for small and large values of the capillary number of the continuous phase revealing the relative contribution of the dispersed phase flow in jet formation. The volume of the drops formed in the jetting regime increased as a power law function of the flow rate ratio of the dispersed to continuous phase, independent of the interfacial tension.

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“…Beyond this, the rate of growth of the neck radius slows down in our CFD simulations due to the presence of the wall. Kovalchuk et al [ 17 ] studied the growth of the neck radius of the doublet in a confined channel with and without the presence of surfactant in the system. Experimental data obtained by Kovalchuk et al [ 17 ] has also been plotted in the figure.…”

Section: Resultsmentioning

confidence: 99%

“…Recently, Kovalchuk et al [ 17 ] studied the coalescence of water droplets in a continuous oil phase in a microfluidic device experimentally using ghost particle velocimetry to understand the effect of surfactant on the droplet coalescence rate, convective flow pattern caused by merging droplets and, the effect of surfactant and drop size on the intensity of convective motion.…”

Section: Introductionmentioning

confidence: 99%

Hydrodynamics of bubble coalescence in microchannels

2020

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Gas‐liquid flow in microchannels is relevant to a number of microfluidic devices without moving parts for application in chemical micro‐processing, inkjet printing, and electronics cooling. Over a large range of gas and liquid flow rates, gas bubbles have the same size as that of the channel. Such bubbles are nearly spherical in shape until their radius is less than that of the channel. The bubbles with a larger volume expand along the axis taking a capsular or bullet shape and are commonly known as Taylor bubbles. For air‐water flow, the spherical bubble is observed to move with a velocity higher than that of the Taylor bubble. In this work, the flow of a Taylor bubble followed by a spherical one, initially separated by several channel diameters, has been studied numerically using the volume of fluid (VOF) method. The hydrodynamics during the bubble approach as well as the evolution of the doublet, that is, the merged bubble, has been investigated. To track the velocity of each bubble with time during the bubble approach stage, a novel methodology has been developed using k‐means clustering algorithm. The evolution of the interface of the doublet has been monitored. The neck radius of the doublet grows as τ0.5, τ being the time since the contact between the bubble interfaces, when the interface is away from the wall. In the near wall region, the radius grows more slowly and is proportional to τ0.1.

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Study of drop coalescence and mixing in microchannel using Ghost Particle Velocimetry

Cited by 16 publications

References 34 publications

The role of valve stiffness in the insurgence of deep vein thrombosis

The role of valve stiffness in the insurgence of deep vein thrombosis

Drop formation in microfluidic cross-junction: jetting to dripping to jetting transition

Hydrodynamics of bubble coalescence in microchannels

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