Title: Lattice Boltzmann simulations of coalescence of two droplets on a rectangular channel wall considering wetting effects

Authors: Saurabh Bhardwaj; Pitambar Randive; Amaresh Dalal

Addresses: Department of Mechanical Engineering, Indian Institute of Technology Guwahati, Guwahati-781039, India ' Department of Mechanical Engineering, National Institute of Technology Silchar, Silchar (Assam)-788010, India ' Department of Mechanical Engineering, Indian Institute of Technology Guwahati, Guwahati-781039, India

Abstract: The present work numerically analyses the interfacial dynamics of coalescence of two droplets on a rectangular channel wall considering wetting effects. The two-phase lattice Boltzmann Shan-Chen model has been incorporated to explore the physics of coalescence of two droplets on channel wall. The main focus of the study is to analyse the time taken by the two droplets to initiate merging into a single droplet and the displacement of immiscible droplets subjected to gravitational forces. The impact of the centre distance between the two droplets (i.e., C_d = 47-55 lu) and capillary number (i.e., Ca = 0.35, 0.50 and 0.81) on droplet dynamics have been examined. The investigation revealed that the two droplets do not merge completely into a single spherical droplet in mixed wettability case but stretched at the junction of hydrophilic and hydrophobic region. It is further revealed that the two droplets coalesce faster on mixed wettable surface compared to uniform hydrophilic surface at a fixed capillary number.

Keywords: immiscible fluids; wettability; capillary number; droplet dynamics; coalescence.

DOI: 10.1504/PCFD.2017.086325

Progress in Computational Fluid Dynamics, An International Journal, 2017 Vol.17 No.5, pp.281 - 289

Received: 25 Jul 2015
Accepted: 29 Apr 2016
Published online: 04 Sep 2017 *

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