Controlled impact of a disk on a water surface: cavity dynamics

Bergmann, Raymond; Meer, Devaraj van der; Gekle, Stephan; Bos, Arjan van der; Lohse, Detlef

doi:10.1017/s0022112009006983

Cited by 151 publications

(147 citation statements)

References 32 publications

(93 reference statements)

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“…To this end, we employ the boundary integral (BI) method described by Bergmann et al (2009);Gekle et al (2010), which has already been successfully used to study drop deformation during mechanical impact (Bouwhuis et al 2012), as well as that due to a laser impact (Klein et al 2015). BI is a powerful method to study the drop dynamics at later times t ∼ τ i , when the drop shape changes significantly.…”

Section: Boundary Integral Simulationsmentioning

confidence: 99%

“…On the intermediate timescale τ i the drop deforms significantly and a purely ballistic approach is no longer applicable. We use in §3 a numerical boundary integral (BI) method (Oguz & Prosperetti 1993;Power & Wrobel 1995;Bergmann et al 2009;Gekle et al 2010;Bouwhuis et al 2012) to confirm the main features of the deformation and the precise detail of the flow. For an unfocussed laser pulse (Fig.…”

Section: Introductionmentioning

confidence: 99%

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Drop deformation by laser-pulse impact

et al. 2016

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A free-falling absorbing liquid drop hit by a nanosecond laser-pulse experiences a strong recoil-pressure kick. As a consequence, the drop propels forward and deforms into a thin sheet which eventually fragments. We study how the drop deformation depends on the pulse shape and drop properties. We first derive the velocity field inside the drop on the timescale of the pressure pulse, when the drop is still spherical. This yields the kinetic-energy partition inside the drop, which precisely measures the deformation rate with respect to the propulsion rate, before surface tension comes into play. On the timescale where surface tension is important the drop has evolved into a thin sheet. Its expansion dynamics is described with a slender-slope model, which uses the impulsive energy-partition as an initial condition. Completed with boundary integral simulations, this two-stage model explains the entire drop dynamics and its dependance on the pulse shape: for a given propulsion, a tightly focused pulse results in a thin curved sheet which maximizes the lateral expansion, while a uniform illumination yields a smaller expansion but a flat symmetric sheet, in good agreement with experimental observations. IntroductionA laser pulse interacting with an absorbing liquid body can deposit a finite amount of energy, concentrated both in time and space, which eventually triggers a dramatic hydrodynamic response. Focused nanosecond pulses have for instance been used to induce cavitation in liquids confined in capillary tubes (Vogel et al. 1996;Sun et al. 2009;Tagawa et al. 2012), or jetting and spraying in sessile drops (Thoroddsen et al. 2009). These situations involving a liquid close to a wall result in localized flows. By contrast, we consider here the situation of a mobile liquid body: the impact of a nanosecond laser pulse onto an absorbing unconfined liquid drop, which, as first described by Klein et al. (2015), has a global hydrodynamic response to the pulse: the drop propels forward at a speed of several meters per second, strongly deforms and eventually fragments (see Fig. 1). This dynamics is similar to that following a mechanical impact such as on a solid substrate or a pillar, which has been studied thoroughly (see e.g. Clanet et al. 2004;Yarin 2006;Villermaux & Bossa 2011;Kolinski et al. 2012;Riboux & Gordillo 2014;Josserand & Thoroddsen 2016), including a few studies on the fragmentation of the drop (Villermaux 2007;Xu et al. 2007;Villermaux & Bossa 2009, 2011Riboux & Gordillo 2014). A laser proves to be an adequate tool to vary the extension of the impact without arXiv:1512.02415v1 [physics.flu-dyn] 8 Dec 2015

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Section: Boundary Integral Simulationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Drop deformation by laser-pulse impact

et al. 2016

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“…We record the events using a Photron SA1 high speed camera. A more detailed description of the experimental setup can be found in Bergmann et al (2009). From now on, distances, times, velocities and pressures are made dimensionless using R D , R D /V D , V D and ρV 2 D as characteristic length, time, velocity and pressure respectively.…”

Section: Experiments and Comparison With Boundary Integral Simulationsmentioning

confidence: 99%

“…The creation and collapse of an underwater cavity has been studied extensively for a solid impacting a liquid surface (Richardson 1948;Gaudet 1998;Lee et al 1997;Bergmann et al 2006;Ducleaux et al 2007;Bergmann et al 2009), as well as the formation of jets resulting from the collapse of this cavity (Longuet-Higgins 1983;Hogrefe et al 1998;Zeff et al 2000;Duchemin et al 2002;Gekle et al 2009;. The first event that is visible after an object hits a liquid is however the splash.…”

Section: Introductionmentioning

confidence: 99%

Splash wave and crown breakup after disc impact on a liquid surface

2013

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In this paper we analyze the impact of a circular disc on a free surface using experiments, potential flow numerical simulations and theory. We focus our attention both on the study of the generation and possible breakup of the splash wave created after the impact and on the calculation of the force on the disc. We have experimentally found that drops are only ejected from the rim located at the top part of the splash -giving rise to what is known as the crown splash-if the impact Weber number exceeds a threshold value We crit ≃ 140. We explain this threshold by defining a local Bond number Bo tip based on the rim deceleration and its radius of curvature, with which we show using both numerical simulations and experiments that a crown splash only occurs when Bo tip 1, revealing that the rim disrupts due to a Rayleigh-Taylor instability. Neglecting the effect of air, we show that the flow in the region close to the disc edge possesses a Weber-numberdependent self-similar structure for every Weber number. From this we demonstrate that Bo tip ∝ We, explaining both why the transition to crown splash can be characterized in terms of the impact Weber number and why this transition occurs for W e crit ≃ 140.Next, including the effect of air, we have developed a theory which predicts the timevarying thickness of the very thin air cushion that is entrapped between the impacting solid and the liquid. Our analysis reveals that gas critically affect the velocity of propagation of the splash wave as well as the time-varying force on the disc, F D . The existence of the air layer also limits the range of times in which the self-similar solution is valid and, accordingly, the maximum deceleration experienced by the liquid rim, what sets the length scale of the splash drops ejected when W e > We crit .

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“…And we marginally expect cavities in the regime of low Reynolds and small Bond numbers. Apart from spheres, the impact of discs has also been studied (Bergmann et al 2010), as well as non-axisymmetric objects (Enriquez et al 2010(Enriquez et al , 2012.…”

Section: Introductionmentioning

confidence: 99%

Explosions at the water surface

2014

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We study the shape and dynamics of cavities created by the explosion of firecrackers at the surface of a large pool of water. Without confinement, the explosion generates a hemispherical air cavity which grows, reaches a maximum size and collapses in a generic w-shape to form a final central jet. When a rigid open tube confines the firecracker, the explosion produces a cylindrical cavity that expands without ever escaping the free end of the tube. We discuss a potential flow model, which captures most of these features.

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Controlled impact of a disk on a water surface: cavity dynamics

Cited by 151 publications

References 32 publications

Drop deformation by laser-pulse impact

Drop deformation by laser-pulse impact

Splash wave and crown breakup after disc impact on a liquid surface

Explosions at the water surface

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