Bridge evolution during the coalescence of immiscible droplets

Abstract

Hypothesis: Droplet coalescence is a common phenomenon and plays an important role in many applications. When two liquid droplets are brought into contact, a liquid bridge forms and expands quickly. Different from miscible droplets, an extra immiscible interface exists throughout the coalescence of immiscible droplets and is expected to affect the evolution of the liquid bridge, which has not been investigated. We hypothesized that the liquid bridge of immiscible droplets exhibits a different growth dynamics. Experiments: We experimentally study the coalescence dynamics of immiscible droplets. The evolution of the liquid bridge is measured and compared with miscible droplets. We also propose a theoretical model to analyze the effects of immiscibility. Findings: We find that immiscibility plays different roles in the viscous-dominated and inertia-dominated regimes. In the initial viscous-dominated regime, the coalescence of immiscible droplets follows the linear evolution of the bridge radius as that of miscible droplets. However, in the later inertia-dominated regime, the coalescence of immiscible droplets is slower than that of miscible droplets due to the water-oil interface. By developing a theoretical model based on the force balance, we show that this slower motion is due to the immiscible interface and the extra interfacial tension. In addition, a modified Ohnesorge number is proposed to characterize the transition from the viscous-dominated regime to the inertia-dominated regime.

References in corpus (9)

• Coalescence of Liquid Drops
• Inviscid coalescence of drops
• Viscous to Inertial Crossover in Liquid Drop Coalescence
• Initial spreading of low-viscosity drops on partially wetting surfaces
• A novel coarsening mechanism of droplets in immiscible fluid mixtures
• Universality in coalescence of polymeric fluid drops
• The Dynamics of Liquid Drops Coalescing in the Inertial Regime
• Rheocoalescence: Relaxation time through coalescence of droplets
• Miscibility and wettability: how interfacial tension influences droplet impact onto thin wall films

Cited by in corpus (5)

• Coalescence of surfactant-laden droplets
• Molecular dynamics simulation of the coalescence of surfactant-laden droplets
• Coalescence of immiscible droplets in liquid environments
• Coalescence of immiscible sessile droplets on a partial wetting surface
• Coalescence of sessile polymer droplets: A molecular dynamics study