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Micro-splashing by drop impacts

Published online by Cambridge University Press:  18 July 2012

S. T. Thoroddsen*
Affiliation:
Division of Physical Sciences and Engineering and Clean Combustion Research Center, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
K. Takehara
Affiliation:
Department of Civil and Environmental Engineering, Kinki University, Higashi-Osaka 577-8502, Japan
T. G. Etoh
Affiliation:
Department of Civil and Environmental Engineering, Kinki University, Higashi-Osaka 577-8502, Japan
*
Email address for correspondence: sigurdur.thoroddsen@kaust.edu.sa

Abstract

We use ultra-high-speed video imaging to observe directly the earliest onset of prompt splashing when a drop impacts onto a smooth solid surface. We capture the start of the ejecta sheet travelling along the solid substrate and show how it breaks up immediately upon emergence from the underneath the drop. The resulting micro-droplets are much smaller and faster than previously reported and may have gone unobserved owing to their very small size and rapid ejection velocities, which approach 100 m s−1, for typical impact conditions of large rain drops. We propose a phenomenological mechanism which predicts the velocity and size distribution of the resulting microdroplets. We also observe azimuthal undulations which may help promote the earliest breakup of the ejecta. This instability occurs in the cusp in the free surface where the drop surface meets the radially ejected liquid sheet.

Type
Papers
Copyright
Copyright © Cambridge University Press 2012

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Thoroddsen et al. supplementary movie

Impact of a water drop viewed through a glass plate. Frame rate: 500,000 fps. Horizontal extent: 3.24 mm. Vertical extent: 3.51 mm. Impact velocity 3.8 m/s. Drop diameter 5.4 mm. We = 1070, Re = 20500.

Download Thoroddsen et al. supplementary movie(Video)
Video 1.5 MB

Thoroddsen et al. supplementary movie

Impact of a water drop viewed through a glass plate. Frame rate: 500,000 fps. Horizontal extent: 3.24 mm. Vertical extent: 3.51 mm. Impact velocity 3.8 m/s. Drop diameter 5.4 mm. We = 1070, Re = 20500.

Download Thoroddsen et al. supplementary movie(Video)
Video 234.3 KB

Thoroddsen et al. supplementary movie

Impact of a water drop viewed through a glass plate. Frame rate: 1,000,000 fps. Horizontal extent: 2.19 mm. Vertical extent: 1.96 mm. Impact velocity 4.8 m/s. Drop diameter 5.5 mm. We = 1740, Re = 26400.

Download Thoroddsen et al. supplementary movie(Video)
Video 1.4 MB

Thoroddsen et al. supplementary movie

Impact of a water drop viewed through a glass plate. Frame rate: 1,000,000 fps. Horizontal extent: 2.19 mm. Vertical extent: 1.96 mm. Impact velocity 4.8 m/s. Drop diameter 5.5 mm. We = 1740, Re = 26400.

Download Thoroddsen et al. supplementary movie(Video)
Video 977.6 KB

Thoroddsen et al. supplementary movie

Impact of a water drop viewed through a glass plate. Frame rate: 250,000 fps. Horizontal extent: 3.68 mm. Vertical extent: 4.50 mm. Impact velocity 5.4 m/s. Drop diameter 6.2 mm. We = 2480, Re = 33500.

Download Thoroddsen et al. supplementary movie(Video)
Video 940 KB

Thoroddsen et al. supplementary movie

Impact of a water drop viewed through a glass plate. Frame rate: 250,000 fps. Horizontal extent: 3.68 mm. Vertical extent: 4.50 mm. Impact velocity 5.4 m/s. Drop diameter 6.2 mm. We = 2480, Re = 33500.

Download Thoroddsen et al. supplementary movie(Video)
Video 142.2 KB

Thoroddsen et al. supplementary movie

Impact of a water drop viewed through a glass plate. Frame rate: 250,000 fps. Horizontal extent: 5.12 mm. Vertical extent: 5.62 mm. Impact velocity 5.4 m/s. Drop diameter 6.2 mm. We = 2480, Re = 33500

Download Thoroddsen et al. supplementary movie(Video)
Video 1.4 MB

Thoroddsen et al. supplementary movie

Impact of a water drop viewed through a glass plate. Frame rate: 250,000 fps. Horizontal extent: 5.12 mm. Vertical extent: 5.62 mm. Impact velocity 5.4 m/s. Drop diameter 6.2 mm. We = 2480, Re = 33500

Download Thoroddsen et al. supplementary movie(Video)
Video 234.7 KB

Thoroddsen et al. supplementary movie

Impact of a water drop viewed through a glass plate. Frame rate: 125,000 fps. Horizontal extent: 5.1 mm. Vertical extent: 5.4 mm. Impact velocity 3.8 m/s. Drop diameter 6.2 mm. We = 1100, Re = 22300

Download Thoroddsen et al. supplementary movie(Video)
Video 2.8 MB

Thoroddsen et al. supplementary movie

Impact of a water drop viewed through a glass plate. Frame rate: 125,000 fps. Horizontal extent: 5.1 mm. Vertical extent: 5.4 mm. Impact velocity 3.8 m/s. Drop diameter 6.2 mm. We = 1100, Re = 22300

Download Thoroddsen et al. supplementary movie(Video)
Video 212 KB