A numerical analysis of air entrapment during droplet impact on an immiscible liquid film

Yeganehdoust, Firoozeh; Attarzadeh, Reza; Karimfazli, Ida; Dolatabadi, Ali

doi:10.1016/j.ijmultiphaseflow.2019.103175

Cited by 38 publications

(18 citation statements)

References 48 publications

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“…Here, σ is the surface tension coefficient, and κ is the interface curvature defined as −∇· n̂ (where n̂ is a unit surface vector). A multiphase flow solver based on the Volume of Fluid (VOF) method in OpenFOAM − is used in conjunction with a modified contact angle model …”

Section: Methodsmentioning

confidence: 99%

Droplet Mobility on Slippery Lubricant Impregnated and Superhydrophobic Surfaces under the Effect of Air Shear Flow

et al. 2021

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The focus of this study is to investigate and compare the behavior of a droplet on superhydrophobic (SHS) and slippery lubricant impregnated (SLIPS) surfaces under the effect of air shear flow. In this regard, both experimental and numerical analyses have been conducted to compare their performance on droplet mobility under different air speeds. Two different lubricants have been utilized to scrutinize their effect on droplet movement. The numerical simulations have been performed based on the volume of fluid method coupled with the large eddy simulation turbulent model in conjunction with the dynamic contact angle method in addition to a model that can represent the effect of lubricants on slippery surfaces. The numerical simulations are compared with the experimental study in order to shed light on the underlying mechanisms. The results showed that under the same conditions, the critical velocity for droplet movement on the superhydrophobic surfaces is lower than that on the slippery lubricant impregnated surfaces due to the smaller droplet base diameter and the larger contact angle. The hydrodynamics of droplet mobility on superhydrophobic surfaces exhibits a rolling behavior while for the slippery lubricant impregnated surfaces a combination of rolling and sliding is observed. Beyond the critical airflow speed, a complete droplet shedding on all surfaces occurs. The wetting length and position of the droplet on superhydrophobic and slippery surfaces have been measured. On slippery surfaces, the speed of droplets is greatly affected by the lubricant properties while similar behavior in the wetting lengths is observed.

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Section: Methodsmentioning

confidence: 99%

Droplet Mobility on Slippery Lubricant Impregnated and Superhydrophobic Surfaces under the Effect of Air Shear Flow

et al. 2021

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“…Similarly, Jian et al 31 examined how variations in the liquid-gas viscosity and density ratios affect the gas cushioning and result in significantly different splashing behaviors. Other works include air cushioning on an immiscible liquid film, 32 heat transfer considerations, 33 and air mediated droplet bouncing. 34 A detailed analytical and numerical study of air entrapment on deformable solid surfaces to complement experimental work 8,9 remains untackled, however.…”

Section: Introductionmentioning

confidence: 99%

Pre-impact dynamics of a droplet impinging on a deformable surface

2021

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The nonlinear interaction between air and a water droplet just prior to a high-speed impingement on a surface is a phenomenon that has been researched extensively and occurs in a number of industrial settings. The role that the surface deformation plays in an air cushioned impact of a liquid droplet is considered here. In a two-dimensional framework, assuming small density and viscosity ratios between the air and the liquid, a reduced system of integrodifferential equations is derived governing the liquid droplet free-surface shape, the pressure in the thin air film, and the deformation of the surface, assuming the effects of surface tension, compressibility, and gravity to be negligible. The deformation of the surface is first described in a rather general form, based on previous membrane-type models. The coupled system is then investigated in two cases: a soft viscoelastic case where the surface stiffness and (viscous) damping are considered and a more general flexible surface where all relevant parameters are retained. Numerical solutions are presented, highlighting a number of key consequences of surface deformability on the pre-impact phase of droplet impact, such as reduction in pressure buildup, increased air entrapment, and considerable delay to touchdown. Connections (including subtle dependence of the size of entrapped air on the droplet velocity, reduced pressure peaks, and droplet gliding) with recent experiments and a large deformation analysis are also presented.

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“…In parallel with experimental studies, some commonly used interface capture methods such as VOF, CLSVOF, Lattice-Boltzmann have been used to show the formation of the air film, but with limited success in capturing the subsequent dynamics, due to the large demand in computation source and the difficulties in establishing surface tension on surfaces with complex microscale topological variations [23][24][25][26][27] . Most of the existing simulation work mainly focuses on the deformation of the droplet before contact, the air pressure distribution in the initial air film, the influence of the air film to the heat transfer between the liquid and the wall, and the influence of the entrapped air to the liquid solidification process, few of them investigates the following air film evolvement dynamics.…”

Section: Introductionmentioning

confidence: 99%