Rheocoalescence: Relaxation time through coalescence of droplets

Abstract

Dynamics of the pendant drop coalescing with a sessile drop to form a single daughter droplet is known to form a bridge. The bridge evolution begins with a point contact between the two drops leading to a liquid neck of size comparable to the diameter of the drops. To probe this phenomenon in polymeric fluids, we quantify the neck radius growth during coalescence using high speed imaging. In the current study, we unveil the existence of three regimes on basis of concentration ratio $c/c^{\ast }$ namely, inertio-elastic $c/c^{\ast }<c_e/c^{\ast }$, viscoelastic $c_e/c^{\ast }<c/c^{\ast }<20$ and elasticity dominated regimes $c/c^{\ast }>20$. Our results suggest that the neck radius growth with time (t) obeys a power-law behaviour $t^b$, such that the coefficient $b$ has a steady value in inertio-elastic and viscoelastic regimes, with a monotonic decrease in elasticity dominated regime. Based on this dependence of $b$ on concentration ratios, we propose a new measurement technique Rheocoalescence to obtain the relaxation time of the these fluids. We also show a deviation from universality proposed in literature for the elasticity dominated regime.

References in corpus (12)

• Coalescence of Liquid Drops
• Inviscid coalescence of drops
• Coalescence of bubbles and drops in an outer fluid
• Viscous to Inertial Crossover in Liquid Drop Coalescence
• The inexorable resistance of inertia determines the initial regime of drop coalescence
• Semidilute Polymer Solutions at Equilibrium and under Shear Flow
• Coalescence of Liquid Drops: Different Models Versus Experiment
• Coalescence in low-viscosity liquids
• Approach and Coalescence of Liquid Drops in Air
• Universality in coalescence of polymeric fluid drops
• Viscous coalescence of droplets: a Lattice Boltzmann study
• Coalescence of polymeric sessile drops on a partially wettable substrate

Cited by in corpus (5)

• Bridge evolution during the coalescence of immiscible droplets
• Elasticity can affect droplet coalescence
• Pinch-off of bubbles in a polymer solution
• Coalescence of viscoelastic drops on a solid substrate
• Coalescence of viscoelastic sessile drops: the small and large contact angle limits