Coalescence of low-viscosity fluids in air

Case, Sarah C.

doi:10.1103/physreve.79.026307

Cited by 36 publications

(50 citation statements)

References 67 publications

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“…In depth analysis indicates that the defect size in particle shells determines the exact merging behaviors: when the defect size is larger than a critical size around the particle diameter, normal coalescence will show up, while abnormal coalescence will appear for coatings with smaller defects. DOI: 10.1103/PhysRevLett.110.064502 PACS numbers: 47.55.df, 47.57.Às When two droplets come into contact, they naturally coalesce to minimize the surface energy, a phenomenon extensively studied since the 19th century [1][2][3][4][5]. A quite recent study reveals that coalescence starts from the regime controlled by inertial, viscous, and surface-tension forces [6], which is followed by either a viscous regime [7] or an inertial regime [8].…”

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confidence: 99%

“…When two droplets come into contact, they naturally coalesce to minimize the surface energy, a phenomenon extensively studied since the 19th century [1][2][3][4][5]. A quite recent study reveals that coalescence starts from the regime controlled by inertial, viscous, and surface-tension forces [6], which is followed by either a viscous regime [7] or an inertial regime [8].…”

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confidence: 99%

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Coalescence of Pickering Emulsion Droplets Induced by an Electric Field

et al. 2013

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Combining high-speed photography with electric current measurement, we investigate the electrocoalescence of Pickering emulsion droplets. Under a high enough electric field, the originally stable droplets coalesce via two distinct approaches: normal coalescence and abnormal coalescence. In the normal coalescence, a liquid bridge grows continuously and merges two droplets together, similar to the classical picture. In the abnormal coalescence, however, the bridge fails to grow indefinitely; instead, it breaks up spontaneously due to the geometric constraint from particle shells. Such connecting-thenbreaking cycles repeat multiple times, until a stable connection is established. In depth analysis indicates that the defect size in particle shells determines the exact merging behaviors: when the defect size is larger than a critical size around the particle diameter, normal coalescence will show up, while abnormal coalescence will appear for coatings with smaller defects. DOI: 10.1103/PhysRevLett.110.064502 PACS numbers: 47.55.df, 47.57.Às When two droplets come into contact, they naturally coalesce to minimize the surface energy, a phenomenon extensively studied since the 19th century [1][2][3][4][5]. A quite recent study reveals that coalescence starts from the regime controlled by inertial, viscous, and surface-tension forces [6], which is followed by either a viscous regime [7] or an inertial regime [8]. However, the coalescence of special droplets-Pickering emulsion droplets-remains poorly understood. Stabilized by colloidal particles instead of surfactant molecules, Pickering emulsions are composed of particle-coated droplets [9,10], as shown in Fig. 1(a). Because of the highly controllable permeability, mechanical strength, and biocompatibility [11][12][13], Pickering emulsions have been actively studied in the last decade, and may find broad applications in important areas such as oil recovery [14] and drug delivery [15]. The wellcontrolled coalescence in Pickering emulsions can also facilitate material mixing and benefit the field of chemical and biochemical assays [16]. More interestingly, the existence of an extra structure-particle shell-may bring fundamentally different merging physics and enrich the classical coalescence research. Consequently, there is great scientific and practical significance to clarifying the coalescence of Pickering emulsion droplets.If the surface is poorly coated, droplets can coalesce spontaneously and form supracolloidal structures [17,18]. Complex dynamics and structure of particles are observed during coalescence, due to the combined effects of charge, surface tension, and liquid flow [19]. Numerical simulation further reveals that the repulsion between particles, the particles' ability to attach to both droplet surfaces, and the stability of the liquid film between droplets are crucial for coalescence behaviors [20]. However, if the surface is coated by closely packed particles, coalescence rarely occurs. Inspired by the strong influence of electric fields, which can d...

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Coalescence of Pickering Emulsion Droplets Induced by an Electric Field

et al. 2013

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“…In this paper, we use an electrical method [7,8] to observe salt water coalescence down to 10 ns after the drops touch. Our measurements are conducted at slow enough approach velocities where no drop deformation occurs.…”

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Viscous to Inertial Crossover in Liquid Drop Coalescence

2011

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Using an electrical method and high-speed imaging we probe drop coalescence down to 10 ns after the drops touch. By varying the liquid viscosity over two decades, we conclude that at sufficiently low approach velocity where deformation is not present, the drops coalesce with an unexpectedly late crossover time between a regime dominated by viscous and one dominated by inertial effects. We argue that the late crossover, not accounted for in the theory, can be explained by an appropriate choice of length-scales present in the flow geometry.

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“…E ects of capillary coe cient and and are two governing parameters in this simulation; they control the interface thickness and surface tension as in Eqs. (16) and (18). Also, the density ratio is governed by as follows:…”

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confidence: 99%

“…Czerski investigated sound during bubble coalescence [15]. Case et al employed an electrical method to study the coalescence of two low-viscosity droplets at early times [16,17]. Aryafar et al used an ultrafast x-ray phase-contrast imaging to investigate the early merging dynamics of two water drops in air [18].…”

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A note on the critical gap of bubble coalescence during foaming process: A diffuse-interface modeling

Rad

2017

Scientia Iranica

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Abstract. Bubble coalescence is an important stage of foaming process. A goal of foaming is to produce numerous, uniform-size bubbles. Therefore, suppression of bubble coalescence is desirable during foaming process. For stationary bubbles, if their distance is less than a critical gap, they will coalesce. Actually, in this case, attractive forces attract the outer surfaces to touch each other and form a growing gas bridge, which nally merges the bubbles. For bigger distance, the attractive forces cannot make a bridge and coalescence will not happen. In this study, the dynamics of bubble coalescence are modeled using a di use-interface LBM. Then, critical gap of bubble coalescence is de ned as the maximum distance between the stationary bubbles where the coalescence will happen. Sensibility of critical gap is obtained with respect to critical properties of material, bubble size, viscosity of gas and liquid, density ratio, surface tension, temperature, and interface thickness. The results show that interface thickness is the only factor that controls the critical gap. In other words, in the case of stationary bubbles, by a precise estimation of interface thickness, the coalescence can be predicted. Critical gap is a useful parameter in foaming where the maximum number of bubbles is desirable.

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Coalescence of low-viscosity fluids in air

Cited by 36 publications

References 67 publications

Coalescence of Pickering Emulsion Droplets Induced by an Electric Field

Coalescence of Pickering Emulsion Droplets Induced by an Electric Field

Viscous to Inertial Crossover in Liquid Drop Coalescence

A note on the critical gap of bubble coalescence during foaming process: A diffuse-interface modeling

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