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Experimental investigation of a liquid droplet onto a granular bed using 3D, time-resolved, particle tracking

Lookup NU author(s): Dr Edward Long, Dr Caspar HewettORCiD


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An experimental investigation into the interaction that occurs between an impacting water droplet and a granular bed of loose graded sand has been carried out. High-speed imaging, three-dimensional time-resolved particle tracking, and photogrammetric surface profiling have been used to examine individual impact events. The focus of the study is the quantification and trajectory analysis of the particles ejected from the sand bed, along with measurement of the change in bed morphology. The results from the experiments have detailed two distinct mechanisms of particle ejection: the ejection of water-encapsulated particles from the edge of the wetted region and the ejection of dry sand from the periphery of the impact crater. That the process occurs by these two distinct mechanisms has hitherto been unobserved. Presented in the paper are distributions of the particle ejection velocities, angles, and transport distances for both mechanisms. The ejected water-encapsulated particles, which are few in number, are characterized by low ejection angles and high ejection velocities, leading to large transport distances; the ejected dry particles, which are much greater in number, are characterized by high ejection angles and low velocities, leading to lower transport distances. From the particle ejection data, the momentum of the individual ballistic sand particles has been calculated; it was found that only 2% of the water-droplet momentum at impact is transferred to the ballistic sand particles. In addition to the particle tracking, surface profiling of the granular bed postimpact has provided detailed information on its morphology; these data have demonstrated the consistent nature of the craters produced by the impact and suggest that particle agglomerations released from their edges make up about twice the number of particles involved in ballistic ejection. It is estimated that, overall, about 4% of the water-droplet momentum is taken up in particle movement.

Publication metadata

Author(s): Long EJ, Hargrave GK, Cooper JR, Kitchener BGB, Parsons AJ, Hewett CJM, Wainwright J

Publication type: Article

Publication status: Published

Journal: Physical Review E

Year: 2014

Volume: 89

Online publication date: 03/03/2014

Acceptance date: 01/02/2014

ISSN (print): 2470-0045

ISSN (electronic): 2470-0053

Publisher: American Physical Society


DOI: 10.1103/PhysRevE.89.032201


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