On the collision of a droplet with a solid surface
08 Jan 1991-Proceedings of The Royal Society A: Mathematical, Physical and Engineering Sciences (The Royal Society)-Vol. 432, Iss: 1884, pp 13-41
TL;DR: In this paper, the collision dynamics of a liquid droplet on a solid metallic surface were studied using a flash photographic method, which provided clear images of the droplet structure during the deformation process.
Abstract: The collision dynamics of a liquid droplet on a solid metallic surface were studied using a flash photographic method. The intent was to provide clear images of the droplet structure during the deformation process. The ambient pressure (0.101 MPa), surface material (polished stainless steel), initial droplet diameter (about 1.5 mm), liquid (n-heptane) and impact Weber number (43) were fixed. The primary parameter was the surface temperature, which ranged from 24 degrees C to above the Leidenfrost temperature of the liquid. Experiments were also performed on a droplet impacting a surface on which there existed a liquid film created by deposition of a prior droplet. The evolution of wetted area and spreading rate, both of a droplet on a stainless steel surface and of a droplet spreading over a thin liquid film, were found to be independent of surface temperature during the early period of impact. This result was attributed to negligible surface tension and viscous effects, and in consequence the measurements made during the early period of the impact process were in good agreement with previously published analyses which neglected these effects. A single bubble was observed to form within the droplet during impact at low temperatures. As surface temperature was increased the population of bubbles within the droplet also increased because of progressive activation of nucleation sites on the stainless steel surface. At surface temperatures near to the boiling point of heptane, a spoke-like cellular structure in the liquid was created during the spreading process by coalescence of a ring of bubbles that had formed within the droplet. At higher temperatures, but below the Leidenfrost point, numerous bubbles appeared within the droplet, yet the overall droplet shape, particularly in the early stages of impact (< 0.8 ms), was unaffected by the presence of these bubbles. The maximum value of the diameter of liquid which spreads on the surface is shown to agree with predictions from a simplified model.
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TL;DR: In this article, a review deals with drop impacts on thin liquid layers and dry surfaces, referred to as splashing, and their propagation is discussed in detail, as well as some additional kindred, albeit nonsplashing, phenomena like drop spreading and deposition, receding (recoil), jetting, fingering, and rebound.
Abstract: The review deals with drop impacts on thin liquid layers and dry surfaces. The impacts resulting in crown formation are referred to as splashing. Crowns and their propagation are discussed in detail, as well as some additional kindred, albeit nonsplashing, phenomena like drop spreading and deposition, receding (recoil), jetting, fingering, and rebound. The review begins with an explanation of various practical motivations feeding the interest in the fascinating phenomena of drop impact, and the above-mentioned topics are then considered in their experimental, theoretical, and computational aspects.
2,077 citations
TL;DR: The fluid dynamic phenomena of liquid drop impact are described and reviewed in this article, and specific conditions under which the above phenomena did occur in experiments are analyzed and the characteristics of drop impact phenomena are described in detail.
1,081 citations
TL;DR: In this article, a model of the deposition-splashing boundary in terms of Reynolds number and Ohnesorge number is presented, which is only achieved if the normal velocity component of the impinging droplets is used in these dimensionless numbers.
1,073 citations
TL;DR: In this article, a numerical solution of the Navier-Stokes equation using a modified SOLA-VOF method was used to model the impact of water droplets on a flat, solid surface using both experiments and numerical simulation.
Abstract: Impact of water droplets on a flat, solid surface was studied using both experiments and numerical simulation. Liquid–solid contact angle was varied in experiments by adding traces of a surfactant to water. Impacting droplets were photographed and liquid–solid contact diameters and contact angles were measured from photographs. A numerical solution of the Navier–Stokes equation using a modified SOLA‐VOF method was used to modeldroplet deformation. Measured values of dynamic contact angles were used as a boundary condition for the numerical model. Impacting droplets spread on the surface until liquid surface tension and viscosity overcame inertial forces, after which they recoiled off the surface. Adding a surfactant did not affect droplet shape during the initial stages of impact, but did increase maximum spread diameter and reduce recoil height. Comparison of computer generated images of impacting droplets with photographs showed that the numerical model modeled droplet shape evolution correctly. Accurate predictions were obtained for droplet contact diameter during spreading and at equilibrium. The model overpredicted droplet contact diameters during recoil. Assuming that dynamic surface tension of surfactant solutions is constant, equaling that of pure water, gave predicted droplet shapes that best agreed with experimental observations. When the contact angle was assumed constant in the model, equal to the measured equilibrium value, predictions were less accurate. A simple analytical model was developed to predict maximum droplet diameter after impact. Model predictions agreed well with experimental measurements reported in the literature. Capillary effects were shown to be negligible during droplet impact when We≫Re1/2.
1,049 citations
TL;DR: In this article, the authors focus on recent experimental and theoretical studies, which aim at unraveling the underlying physics, characterized by the delicate interplay of liquid inertia, viscosity, and surface tension, but also the surrounding gas.
Abstract: A drop hitting a solid surface can deposit, bounce, or splash. Splashing arises from the breakup of a fine liquid sheet that is ejected radially along the substrate. Bouncing and deposition depend crucially on the wetting properties of the substrate. In this review, we focus on recent experimental and theoretical studies, which aim at unraveling the underlying physics, characterized by the delicate interplay of not only liquid inertia, viscosity, and surface tension, but also the surrounding gas. The gas cushions the initial contact; it is entrapped in a central microbubble on the substrate; and it promotes the so-called corona splash, by lifting the lamella away from the solid. Particular attention is paid to the influence of surface roughness, natural or engineered to enhance repellency, relevant in many applications.
994 citations
Cites methods from "On the collision of a droplet with ..."
...…parameters have been established using physical argument based in general on the balance between inertia, viscous and capillary contributions (Chandra & Avedisian (1991); Clanet et al. (2004); Eggers et al. (2010); Fedorchenko et al. (2005); Pasandideh-Fard et al. (1996); Roisman et al.…...
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...This bubble was observed in the snapshots of Chandra & Avedisian (1991), Thoroddsen & Sakakibara (1998) and under inkjet droplets by Van Dam & Le Clerc (2004), but without clear explanation of its formation....
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TL;DR: Benard as mentioned in this paper observed a cellular deformation produced on the free surface of a liquid film the bottom surface of which (in contact with a floor) was uniformly heated and hotter than its top surface.
Abstract: IN 1900, Benard1 described his observations of a cellular deformation produced on the free surface of a liquid film the bottom surface of which (in contact with a floor) was uniformly heated and hotter than its top surface. He also observed a cellular flow associated with the deformation. These studies were made on films of thicknesses in the range 0.5–1.0 mm.
352 citations
TL;DR: In this article, a critical compilation of the homogeneous nucleation limits of liquids is provided, where data for 90 pure substances and 28 mixtures have been compiled over a range of pressures, nucleation rates, and compositions.
Abstract: This work provides a critical compilation of the homogeneous nucleation limits of liquids. Data for 90 pure substances and 28 mixtures have been compiled over a range of pressures, nucleation rates, and compositions. Detailed descriptions of the experimental methods used to obtain the included data are given to assess the accuracy of measured values. Criteria used to select the measurements included in the final listing are discussed.
240 citations
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