Impact of a drop onto a wetted wall: description 
of crown formation and propagation

Roisman, Ilia V.; Tropea, Cameron

doi:10.1017/s0022112002002434

Cited by 195 publications

(90 citation statements)

References 16 publications

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“…The relationship proposed by Fedorchenko and Wang (2004) relating the crown angle to the non-dimensional film thickness was criticised by Yarin (2006). The relationship proposed by Roisman and Tropea (2002) is quite detailed but requires prior knowledge of the liquid film and crown velocities and thicknesses and is therefore difficult to confirm even for droplet impingement on flat surfaces. While the determination of the magnitude of the crown angle is difficult for droplet impingement on a flat surface, it is possible to argue how the crown angle will develop on a curved surface, as in the case of a particle, in relation to the crown angle of a droplet impact on a flat surface.…”

Section: Onset Of Instability On the Crown Rimmentioning

confidence: 99%

Collisions of droplets on spherical particles

Charalampous

Hardalupas

2017

Physics of Fluids

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Head-on collisions between droplets and spherical particles are examined for water droplets in the diameter range between 170 μm and 280 μm and spherical particles in the diameter range between 500 μm and 2000 μm. The droplet velocities range between 6 m/s and 11 m/s, while the spherical particles are fixed in space. The Weber and Ohnesorge numbers and ratio of droplet to particle diameter were between 92 < We < 1015, 0.0070 < Oh < 0.0089, and 0.09 < Ω < 0.55, respectively. The droplet-particle collisions are first quantified in terms of the outcome. In addition to the conventional deposition and splashing regimes, a regime is observed in the intermediate region, where the droplet forms a stable crown, which does not breakup but propagates along the particle surface and passes around the particle. This regime is prevalent when the droplets collide on small particles. The characteristics of the collision at the onset of rim instability are also described in terms of the location of the film on the particle surface and the orientation and length of the ejected crown. Proper orthogonal decomposition identified that the first 2 modes are enough to capture the overall morphology of the crown at the splashing threshold.

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Section: Onset Of Instability On the Crown Rimmentioning

confidence: 99%

Collisions of droplets on spherical particles

Charalampous

Hardalupas

2017

Physics of Fluids

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“…Following the approach in Roisman and Tropea [22] for a jet projection from the kinetic discontinuity between the lower and upper layers with thickness ranging from h 1 to h 2 and velocity from v 1 to v 2 (see figure 5 e), the mean velocity vector of the jet,…”

Section: (A) Wave Impactsmentioning

confidence: 99%

Transverse instabilities of ascending planar jets formed by wave impacts on vertical walls

Watanabe

Ingram

2015

Proc. R. Soc. A.

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When a steep breaking wave hits a vertical sea wall, in shallow water, a rapidly ascending planar jet forms. This jet is ejected with high acceleration due to pressure created by the violent wave impact on the wall, creating a so-called ‘flip-through’ event. Previous studies have focused on the impulsive pressures on, and within, the wall and on the velocity of the jet. Here, in contrast, we consider the formation and break-up of the jet itself. Experiments show that during flip-through a fluid sheet, bounded by a rim, forms. This sheet has unstable transitional behaviours and organizing jets; undulations in the thickness of the fluid sheet are rapidly amplified and ruptured into an array of vertical ligaments. Lateral undulations of the rim lead to the formation of finger-jets, which subsequently break up to form droplets and spray. We present a linear stability analysis of the rim–sheet systems that highlights the contributions of rim retraction and sheet stretching to the break-up process. The mechanisms for the sequential surface deformations in the rim–sheet system are also described. Multiple, distinct, instability modes are identified during the rim deceleration, sheet stretch attenuation and rim retraction processes. The wavenumbers (and deformation length scales) associated with these instability modes are shown to lead to the characteristic double peak spectrum of surface displacement observed in the experiments. These mechanisms help to explain the columnar structures often seen in photographs of violent wave impacts on harbour walls.

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“…In the case of splashing a radial expanding flow in the lamella is formed after the drop impact. Due to the interaction with the outer liquid wall film an uprising liquid sheet is generated which is bounded by a Taylor rim [10][11][12]. If the rim gets unstable, finger-like jets are formed which lead to the generation of secondary drops [14].…”

Section: Introductionmentioning

confidence: 99%

Splashing of a very viscous liquid drop impacting onto a solid wall wetted by another liquid

Kittel

Roisman

2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

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In this experimental work the main focus is on the impact of a single drop of a very viscous liquid onto a thin, horizontal wall film of different liquid. Splashing resulting from drop impact onto a wetted wall occurs in many natural and engineering applications like in internal combustion engines and spray cooling. While the splashing threshold for low viscosity liquid drops has been extensively examined, impact of a very viscous drop is much less studied. The viscosities of drop and wall film liquids are varied up to kinematic viscosities of 100,000 mm²/s. The liquids used in the experiments are miscible. The impact outcome is determined by the impact parameters and fluid properties. The effect of very viscous liquids used as drop fluid and as wall film liquid on the kinematic of the corona expansion is investigated in the experiments. The results of drop impact onto solid walls are compared to obtain the limiting asymptotic values for the splashing threshold. Finally, a semi-empirical model for the splashing threshold, for the maximum spreading radius Dmax and for the maximum spreading times tmax are developed for extremely viscous liquids. Keywords Drop impact, high viscous liquids, wetted wall IntroductionSplashing as a result of a drop impact onto a thin liquid film [1][2][3] or onto a dry substrate [4-6] occurs in many natural and engineering applications like spray coating, spray cooling, paint spraying, ink-jet printing and in internal combustion engines. Impact of a supercooled drop onto a surface of an aircraft can lead to ice accretion, while collision with a heated substrate can lead to drop evaporation or intensive boiling [7]. The drop/wall interaction is affected by the fact that the drop and the liquid film are different liquids and may exhibit different degrees of miscibility and viscosity. A comprehensive review on the phenomena, modeling and application of drop impact can be found in [8]. Drop impact onto a wetted wall can lead to various different outcomes. In the case of splashing

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Impact of a drop onto a wetted wall: description of crown formation and propagation

Cited by 195 publications

References 16 publications

Collisions of droplets on spherical particles

Collisions of droplets on spherical particles

Transverse instabilities of ascending planar jets formed by wave impacts on vertical walls

Splashing of a very viscous liquid drop impacting onto a solid wall wetted by another liquid

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