Analysis of partial electrocoalescence by Level-Set and finite element methods

Vivacqua, Vincenzino; Ghadiri, Mojtaba; Abdullah, Aboubakr M.; Hassanpour, Ali; Al–Marri, Mohammed J.; Azzopardi, B.J.; Kermani, Bijan

doi:10.1016/j.cherd.2016.08.019

Cited by 34 publications

(13 citation statements)

References 28 publications

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“…The ions accumulated on the droplet interface migrate onto the adjacent interface of the droplets. As a result, Coulombic repulsion F 2 , which is proportional to the droplet conductivity, appears between identical ions, as shown in Figure c. Moreover, the ionic migration also results in droplets with opposite charges Q . , The two droplets are then subjected to opposite electrostatic forces F 1 ′, which is proportional to QE …”

Section: Results and Discussionmentioning

confidence: 98%

Electrocoalescence Criterion of Conducting Droplets Suspended in a Viscous Fluid

et al. 2019

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Coalescence of conducting droplets dispersed in an immiscible medium can be facilitated by an electric field. However, droplets recoil promptly after contact in sufficiently high electric fields if the cone angle between droplets exceeds a critical value. To elucidate the critical condition for droplet coalescence, the behavior of two suspended droplets after contact with a direct current electric field is studied. It is shown that the critical angle is determined not only by the droplet geometry but also conductivity, surfactant concentration, and size. As the droplet conductivity increases, more identical ions accumulate on the adjacent interfaces of two droplets due to the faster ionic migration, which results in Coulombic repulsion between droplets and a reduced critical angle. For surfactant-laden droplets, film drainage induces a surfactant concentration gradient on the leading edges of droplets, and then Marangoni stress is formed to reduce the critical angle. In the case of large droplets, the bridge transiently expands under the action of directional flow caused by further droplet deformation, but eventually breaks due to opposite electrostatic forces. Based on this finding, the electrocoalescence criterion can be determined and employed to facilitate droplet coalescence in various applications.

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Section: Results and Discussionmentioning

confidence: 98%

Electrocoalescence Criterion of Conducting Droplets Suspended in a Viscous Fluid

et al. 2019

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“…The primary advantage of the LSM lies in its accurate computation of two-phase flows with complex topological changes. 17 It has been applied to simulate the single bubble boiling behavior, 18 the coalescence of a water droplet in an oil phase, 19 the free rising droplet, 20 etc. In a previous study of our group, 21 this method was adopted to simulate the jet velocity in the electrospinning process.…”

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confidence: 99%

Simulation of jet velocity in the melt-blowing process using the coupled air–polymer model

Hao

Huang

Zeng

2018

Textile Research Journal

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The polymer jet velocity is one of the most basic and critical factors in the melt-blowing process and has always been difficult to measure online. Much effort has been made on the numerical prediction of the jet velocity. However, little work has involved the complex interaction between the air flow and the polymer. Here, the Level-Set method is used to develop the coupled air–polymer two-phase flow model, and to simulate the polymer jet motion in the melt-blowing process considering the coupled effect of the air and polymer. Meanwhile, high-speed photography is adopted in the experiments to verify the simulation results. The x- and y-components of the jet velocities and the whipping amplitude of the jet motion are discussed. The rapid increase of jet velocity and the decrease of jet diameter show that most attenuation of the polymer jet occurred within a distance close to the die (10 mm). Based on the model, the effects of the processing parameters on the jet velocity are examined numerically.

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“…The selection of the most suitable electric field parameters for the optimisation of the process efficiency therefore depends on a trade-off between enhancing the coalescence kinetics and preventing secondary droplet formation. However, the occurrence of partial coalescence it is likely to be also dependent on other factors, such as the mechanism of charge relaxation (Vivacqua et al, 2016).…”

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confidence: 99%

Linear dynamics modelling of droplet deformation in a pulsatile electric field

Vivacqua

Ghadiri

Abdullah

et al. 2016

Chemical Engineering Research and Design

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Resonance is possible only when the droplets are sufficiently large (i.e. for Ohnesorge number less than 1). The oscillation amplitude decreases rapidly with the electric field frequency. A qualitative comparison with some experiments of droplet-interface coalescence available in the literature has also been addressed, suggesting a correlation between the formation of secondary droplets and the amplitude of oscillation of the mother droplet. The outcomes of this analysis can be useful for the selection of the best operating conditions to improve the electrocoalescence process efficiency, as they can provide guidelines to the choice of the most suitable electric field parameters.

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Analysis of partial electrocoalescence by Level-Set and finite element methods

Cited by 34 publications

References 28 publications

Electrocoalescence Criterion of Conducting Droplets Suspended in a Viscous Fluid

Electrocoalescence Criterion of Conducting Droplets Suspended in a Viscous Fluid

Simulation of jet velocity in the melt-blowing process using the coupled air–polymer model

Linear dynamics modelling of droplet deformation in a pulsatile electric field

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