Single drop impact onto liquid films: 

neck distortion, jetting, tiny bubble entrainment, 

and crown formation

Weiss, Daniel; Yarin, Alexander L.

doi:10.1017/s002211209800411x

Cited by 233 publications

(144 citation statements)

References 23 publications

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“…Considering a millimetric drop impacting at a velocity of the order of 10 m.s −1 representative of e.g. a raindrop falling at terminal velocity, we reckon that acoustic effects matter only in a micron-sized region over a few nanoseconds (see Weiss & Yarin 1999, for a discussion and references). The following discussion will therefore be limited to those cases where the impact velocity is much lower than the speed of sound, as the falling raindrop, where acoustic effects can harmlessly be neglected and an incompressible description remains accurate.…”

Section: Theoretical Framework and Hypothesesmentioning

confidence: 99%

Drop impact on a solid surface: short-time self-similarity

2016

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The early stages of drop impact onto a solid surface are considered. Detailed numerical simulations and detailed asymptotic analysis of the process reveal a self-similar structure both for the velocity field and the pressure field. The latter is shown to exhibit a maximum not near the impact point, but rather at the contact line. The motion of the contact line is furthermore shown to exhibit a 'tank treading' motion. These observations are apprehended at the light of a variant of Wagner theory for liquid impact. This framework offers a simple analogy where the fluid motion within the impacting drop may be viewed as the flow induced by a flat rising expanding disk. The theoretical predictions are found to be in very close agreement both qualitatively and quantitatively with the numerical observations for about three decades in time. Interestingly the inviscid self-similar impact pressure and velocities are shown to depend solely on the self-similar variables (r/ √ t, z/ √ t). The structure of the boundary layer developing along the wet substrate is investigated as well, and is proven to be formally analogous to that of the boundary layer growing in the trail of a shockwave. Interestingly, the boundary layer structure only depends on the impact self-similar variables. This allows to construct a seamless uniform analytical solution encompassing both impact and viscous effects. The depiction of the different dynamical fields enables to quantitatively predict observables of interest, such as the evolution of the integral viscous shearing force and of the net normal force. IntroductionThe impact of a liquid drop onto a rigid surface results in a rapid sequence of events ending, in the inertial limit, in spreading (Eggers et al. 2010) or splashing (Stow & Hadfield 1981), interface tearing (Villermaux & Bossa 2011) and ultimate fragmentation (Stow & Stainer 1977). A large number of studies have investigated the many facets of drop impact, with a special attention to the description of its late stages (Rein 1993;Yarin & Weiss 1995). The literature on the early stages of impact is however scarce in comparison. Detailed experimental data depicting the instants following impact can nonetheless be found in the work of Rioboo et al. (2002), that evidenced a "kinematic phase" where the drop merely resembles a truncated sphere and spreads as the squareroot of time. This phase precedes the apparition of the liquid lamella.Probably one of the first depiction of the very first instants of drop impact dates back to Engel (1955). With the help of high-speed cinematography, Engel captured the chronology of events triggered by drop impact. He noted in particular the unvarying shape of the drop apex during the earliest moments of impact, which might be surprising due to the incompressible character of the liquid. Engel put forward the possible roles of inertia, viscosity or surface tension to explain this observation. Actually, the physical mechanism underpinning this behaviour is best illustrated with Figure 1a. There, the numerically...

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Section: Theoretical Framework and Hypothesesmentioning

confidence: 99%

Drop impact on a solid surface: short-time self-similarity

2016

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“…In this paper we describe the asymptotic solution in stages (i)-(iii), thereby identifying the mechanics of the formation of the splash jet before the droplet undergoes global deformation in stage (iv), which must inevitably be treated numerically as described in Josserand & Zaleski (2003), Purvis & Smith (2004, 2005, Weiss & Yarin (1999) and references therein. We find that stage (ii) is in fact a special case of a bona fide temporal intermediate regime between stages (i) and (iii), which is valid for all times t such that 2 t 2/3 .…”

Section: Asymptotic Developmentmentioning

confidence: 99%

Droplet impact on a thin fluid layer

Howison¹,

Ockendon²,

Oliver

et al. 2005

J. Fluid Mech.

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The initial stages of high-velocity droplet impact on a shallow water layer are described, with special emphasis given to the spray jet mechanics. Four stages of impact are delineated, with appropriate scalings, and the successively more important influence of the base is analysed. In particular, there is a finite time before which part of the water in the layer remains under the droplet and after which all of the layer is ejected in the splash jet.

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“…In particular Thoroddsen provides evidence of the formation of a fast moving horizontal jet in the early stages of the impact which was to prove supportive to work on modelling droplet impact. Weiss and Yarin (1999) provide a numerical study of a single water droplet impact onto a film of the same liquid. They consider surface tension and gravity but not viscosity or compressibility.…”

Section: Introductionmentioning

confidence: 99%