Effect of radius ratios of two droplets on coalescence-induced self-propelled jumping

Yuhang Wang,Pingjian Ming

doi:10.1063/1.5034235

Abstract

The coalescence-induced self-propelled droplet jumping behaviors on superhydrophobic surfaces have attracted extensive interest, due to a huge application potential. The coalescence and jumping of two droplets with different radius ratios are numerically simulated, and the jumping velocity is theoretically analyzed. The jumping type changes from the vertical motion to the upward rotation motion, with the decrease of radius ratio. The droplet is not able to jump when the radius ratio is smaller than 0.4. The jumping velocity reaches several peak values when the radius ratio is smaller than 0.7. The maximum jumping velocities are theoretically predicted, which is based on the law of conservation of energy. The viscous dissipation energy which should not be ignored is the main and direct source of the errors.

Highlights

The coalescence-induced self-propelled jumping behaviors have been observed in natural materials.[1,2,3,4]
In the aspect of numerical simulation, the lattice Boltzmann method (LBM),[40,41,42,43] the 3D volume of fluid (VOF) method,[44,45] the phase field method[46] and the molecular simulation[47] were applied to study the coalescence-induced self-propelled jumping of the droplets with equal radii
Wang et al focused on the critical size ratio for droplet jumping, considering the influence of the contact angle.[49]

Summary

Introduction

The coalescence-induced self-propelled jumping behaviors have been observed in natural materials.[1,2,3,4] Inspired by the structures of these natural materials, the jumping behaviors have been achieved on fabricated surfaces which have nanostructures or hierarchical micro-/nanostructures,[5,6,7,8,9,10,11,12,13,14,15,16,17] and been demonstrated for industrial applications, such as self-cleaning,[4,18,19,20] anti-ice[21,22,23,24,25] and condensation heat transfer enhancement.[26,27,28,29,30,31,32,33] the issue of coalescence-induced self-propelled droplet jumping has received significant attention in recent years. Effect of radius ratios of two droplets on coalescence-induced self-propelled jumping Yuhang Wang and Pingjian Minga College of Power and Energy Engineering, Harbin Engineering University, Harbin 150001, China (Received 10 April 2018; accepted 18 June 2018; published online 26 June 2018)

Results

Conclusion