Symmetric and Asymmetric Coalescence of Polymeric Droplets: Effect of Weber number and Viscosity

Understanding droplet dynamics (e.g., impact, spreading, coalescence, etc.) is key to understand the deposition process of any droplet based direct-write printing processes such as Aerosol Jet printing (AJP) and inkjet printing (IJP). In this study, we employ direct numerical simulations for probing the coalescence dynamics of two equal-sized (case of symmetric coalescence) as well as two unequal-sized (case of asymmetric coalescence) polymeric liquid droplets impacting on a solid substrate. We investigate the effect of Weber number and the liquid viscosity on the coalescence dynamics, which in turn is quantified by time evolution of the height (h₀) and width (W) of the bridge formed by the coalescing droplets. The numerical results dictating this growth of the height and the width of the bridge are established to obey distinct physics-based scaling laws.