Drop coalescence through a liquid/liquid interface

Abstract

PIV experiments were conducted to study the coalescence of single drops through planar liquid/liquid interfaces. Sequences of velocity vector fields were obtained with a highspeed video camera and subsequent PIV analysis. Two ambient liquids with different viscosity but similar density were examined resulting in Reynolds numbers based on a surface tension velocity of 10 and 26. Prior to rupture, the drops rested on a thin film of ambient liquid above an underlying interface. After rupture, which was typically offaxis, the free edge of the thin film receded rapidly allowing the drop fluid to sink into the bulk liquid below. Vorticity generated in the collapsing fluid developed into a vortex ring straddling the upper drop surface. The ring core traveled radially inward with a ringshaped capillary wave effectively pinching the upper drop surface and increasing the drop collapse speed. The inertia of the collapse deflected the interface downward before it rebounded upward. During this time, the vortex core split so that part of its initial vorticity moved inside the drop fluid while part remained in the ambient fluid above it. A second ring-shaped capillary wave formed along the interface outside of the drop and propagated radially outward during the collapse. Changing the ambient fluid viscosity resulted in several effects. First, the velocity of the receding free edge was smaller for

Thermal delay of drop coalescence

“…has been characterized (e.g. Charles & Mason 1960a,b;Jeffreys & Davis 1971), leading to a classification of different dynamical regimes (Aryafar & Kavehpour 2006 in high-speed imaging (Thoroddsen & Takehara 2000), experimental techniques (Mohamed-Kassim & Longmire 2004), and numerical simulations (Blanchette & Bigioni 2006) have furthered our understanding of coalescence in various circumstances, including the effects of concentration-induced Marangoni stresses (Blanchette, Messio & Bush 2009). The myriad aspects of coalescence were recently reviewed by Kavehpour (2015).…”

Experimental investigations of non‐Newtonian/Newtonian liquid‐liquid flows in microchannels

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Toward a new experimental method for measuring coalescence in bitumen emulsions: A study of two bitumen droplets

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