Numerical investigation of elongated drops in a microfluidic T-junction

Afkhami, Shahriar; Leshansky, Alexander; Renardy, Yuriko

doi:10.1063/1.3549266

Cited by 79 publications

(50 citation statements)

References 32 publications

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“…Figure 3(a) shows the evolution of neck thickness for both the two-and three-dimensional simulations. In agreement with Leshansky et al (2012), we find that in two dimensions the thickness of the neck decreases monotonically until a grid-dependent collapse (a consequence of the VOF method, see also Afkhami, Leshansky & Renardy 2011). The 3/7 scaling describes the data well, as shown in the inset.…”

Section: Dynamics Of Droplet Breakup In a T-junctionsupporting

confidence: 69%

Dynamics of droplet breakup in a T-junction

et al. 2013

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The breakup of droplets due to creeping motion in a confined microchannel geometry is studied using three-dimensional numerical simulations. Analogously to unconfined droplets, there exist two distinct breakup phases: (i) a quasi-steady droplet deformation driven by the externally applied flow; and (ii) a surface-tension-driven three-dimensional rapid pinching that is independent of the externally applied flow. In the first phase, the droplet relaxes back to its original shape if the externally applied flow stops; if the second phase is reached, the droplet will always break. Also analogously to unconfined droplets, there exist two distinct critical conditions: (i) one that determines whether the droplet reaches the second phase and breaks, or it reaches a steady shape and does not break; and (ii) one that determines when the rapid autonomous pinching starts. We analyse the second phase using stop-flow simulations, which reveal that the mechanism responsible for the autonomous breakup is similar to the end-pinching mechanism for unconfined droplets reported in the literature: the rapid pinching starts when, in the channel mid-plane, the curvature at the neck becomes larger than the curvature everywhere else. The same critical condition is observed in simulations in which we do not stop the flow: the breakup dynamics and the neck thickness corresponding to the crossover of curvatures are similar in both cases. This critical neck thickness depends strongly on the aspect ratio, and, unlike unconfined flows, depends only weakly on the capillary number and the viscosity contrast between the fluids inside and outside the droplet.

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Section: Dynamics Of Droplet Breakup In a T-junctionsupporting

confidence: 69%

Dynamics of droplet breakup in a T-junction

et al. 2013

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“…Although derived for the 2D case, the boundary condition (7) suitably agrees with our 3D simulations and other experimental results [17].…”

Section: Junction Crossingsupporting

confidence: 74%

Introducing purely hydrodynamic networking mechanisms in microfluidic systems

Biral

Zanella

2013

2013 IEEE International Conference on Communications Workshops (ICC)

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Abstract-Microfluidic is a multidisciplinary field with practical applications to the design of systems, called Lab-on-aChip (LoC), where tiny volumes of fluids are circulated through channels with millimeter size and driven into structures where precise chemical/physical processes take place. One subcategory of microfluidic is droplet-based microfluidic, which disperse discrete volumes of fluids into a continuous stream of another immiscible fluid, which act as droplet carrier. Droplets can then be moved, merged, split, or processed in many other ways by suitably managing the hydrodynamic parameters of the LoC. A very interesting research challenge consists in developing basic microfluidic structures able to interconnect specialized LoCs by means of a flexible and modular microfluidic network. The aim of this paper is to exploit the properties of dropletbased microfluidics to realize purely hydrodynamic microfluidic elements that provide basic networking functionalities, such as addressing and switching. We define some simple mathematical models that capture the macroscopic behavior of droplets in microfluidic networks and use such models to design and analyze a simple microfluidic network system with bus topology.

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“…respectively 19 . Similar scaling relations have also been derived for moving foams as well as bubble trains in micro-devices 32 .…”

Section: D Simulations Of Droplet Migration In a Microchannelmentioning

confidence: 99%

“…Numerical simulations which provide a complete description of the flow field can shed light on the present problem. It has been shown that numerical approximations of the Navier-Stokes equations can represent flow physics in many microfluidics applications, such as droplets/bubbles migration and the breakup of droplets at T-junctions [19][20][21][22] .…”

Section: Introductionmentioning

confidence: 99%

Droplet migration in a Hele–Shaw cell: Effect of the lubrication film on the droplet dynamics

et al. 2016

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Droplet migration in a Hele-Shaw cell is a fundamental multiphase flow problem which is crucial for many microfluidics applications. We focus on the regime at low capillary number and three-dimensional direct numerical simulations are performed to investigate the problem. In order to reduce the computational cost, an adaptive mesh is employed and high mesh resolution is only used near the interface. Parametric studies are performed on the droplet horizontal radius and the capillary number.For droplets with an horizontal radius larger than half the channel height the droplet overfills the channel and exhibits a pancake shape. A lubrication film is formed between the droplet and the wall and particular attention is paid to the effect of the lubrication film on the droplet velocity. The computed velocity of the pancake droplet is shown to be lower than the average inflow velocity, which is in agreement with experimental measurements. The numerical results show that both the strong shear induced by the lubrication film and the three-dimensional flow structure contribute to the low mobility of the droplet. In this low-migration-velocity scenario the interfacial flow in the droplet reference frame moves toward the rear on the top and reverses direction moving to the front from the two side edges. The velocity of the pancake droplet and the thickness of the lubrication film are observed to decrease with capillary number. The droplet velocity and its dependence on capillary number cannot be captured by the classic Hele-Shaw equations, since the depth-averaged approximation neglects the effect of the lubrication film.

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Numerical investigation of elongated drops in a microfluidic T-junction

Cited by 79 publications

References 32 publications

Dynamics of droplet breakup in a T-junction

Dynamics of droplet breakup in a T-junction

Introducing purely hydrodynamic networking mechanisms in microfluidic systems

Droplet migration in a Hele–Shaw cell: Effect of the lubrication film on the droplet dynamics

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