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Bounce regime of droplet collisions: A molecular dynamics study

Zhang, YR; Jiang, XZ; Luo, KH; (2016) Bounce regime of droplet collisions: A molecular dynamics study. Journal of Computational Science , 17 (2) pp. 457-462. 10.1016/j.jocs.2016.03.011. Green open access

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Abstract

Droplet collisions have complex dynamics, which can lead to many different regimes of outcomes. The head-on collision and bounce back regime has been observed in previous experiments but numerical simulations using macro- or mesoscale approaches have difficulties reproducing the phenomena, because the interfacial regions are not well resolved. Previous molecular dynamics (MD) simulations have not reproduced the bounce regime either but have reported the coalescence and/or shattering regimes. To scrutinize the dynamics and mechanisms of binary collisions especially the interfacial regions, head-on collision processes of two identical nano-droplets with various impact velocities both in vacuum and in an ambient of nitrogen gas are investigated by MD simulations. With the right combination of the impact velocity and ambient pressure, the head-on collision and bounce back phenomenon is successfully reproduced. The bounce phenomena are mainly attributed to the “cushion effect” of the in-between nitrogen molecules and evaporated water molecules from the two nano-droplets. The analysis has verified and also extended the current gas film theory for the bounce regime through including the effects of evaporated water molecules (vapour). Some similarities and some dissimilarities between nanoscale and macro-/meso-/microscale droplet collisions have been observed. The study provides unprecedented insight into the interfacial regions between two colliding droplets.

Type: Article
Title: Bounce regime of droplet collisions: A molecular dynamics study
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/j.jocs.2016.03.011
Publisher version: http://dx.doi.org/10.1016/j.jocs.2016.03.011
Language: English
Additional information: Copyright © 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Keywords: Multiphase flow; Binary droplet collision; Nanoscale; Molecular dynamics; Droplet bounce
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Mechanical Engineering
URI: https://discovery.ucl.ac.uk/id/eprint/1501089
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