Progress in Computational Fluid Dynamics, Vol. 17, No. 5, 2017 281 Lattice Boltzmann simulations of coalescence of two droplets on a rectangular channel wall considering wetting effects Saurabh Bhardwaj Department of Mechanical Engineering, Indian Institute of Technology Guwahati, Guwahati-781039, India Email: saurabh.2014@iitg.ernet.in Pitambar Randive Department of Mechanical Engineering, National Institute of Technology Silchar, Silchar (Assam)-788010, India Email: kp691975@gmail.com Amaresh Dalal* Department of Mechanical Engineering, Indian Institute of Technology Guwahati, Guwahati-781039, India Email: amaresh@iitg.ernet.in *Corresponding author 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. Reference to this paper should be made as follows: Bhardwaj, S., Randive, P. and Dalal, A. (2017) ‘Lattice Boltzmann simulations of coalescence of two droplets on a rectangular channel wall considering wetting effects’, Progress in Computational Fluid Dynamics, Vol. 17, No. 5, pp.281–289. Biographical notes: Saurabh Bhardwaj is currently pursuing his PhD in Mechanical Engineering at Indian Institute of Technology Guwahati. He received his Masters in Fluid and Thermal Engineering from IIT Guwahati in 2013. His research interests include computational fluid dynamics and heat transfer, natural convection flows inside porous and non-porous enclosures with or without nano-fluids and lattice Boltzmann methods in multiphase-multicomponent flows. Pitambar Randive is currently an Assistant Professor in the Department of Mechanical Engineering, National Institute of Technology Silchar, India. He received his Masters degree in Heat Power Engineering from NIT Nagpur, India in 2001 and PhD from IIT Guwahati in 2014. His research interests include mesoscopic modelling of multiphase flows and natural convection heat transfer. Amaresh Dalal is currently an Associate Professor in the Department of Mechanical Engineering, Indian Institute of Technology Guwahati, India. He received his Masters degree in Fluid and Thermal Engineering from IIT Guwahati in 2003 and PhD from IIT Kanpur in 2009. He was also post-doctoral research associate at Purdue University from 2008–2009. His research interests are computational fluid dynamics and heat transfer, structured grid techniques in Copyright © 2017 Inderscience Enterprises Ltd.