Journal ArticleDOI
On the collision of a droplet with a solid surface
Sanjeev Chandra,C.T. Avedisian +1 more
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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.read more
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References
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Journal ArticleDOI
Surface Tension as the Cause of Bénard Cells and Surface Deformation in a Liquid Film
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.
Journal ArticleDOI
The Homogeneous Nucleation Limits of Liquids
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.
Journal ArticleDOI