Observation of Droplet Size Oscillations in a Two-Phase Fluid under Shear Flow

TL;DR

This paper reports experimental observations of sustained droplet size oscillations in a two-phase fluid under shear flow, revealing complex dynamics and transitions between steady states influenced by shear rate.

Contribution

It introduces the first experimental evidence of droplet size oscillations in a two-phase flow under shear, highlighting the transition mechanisms between different steady states.

Findings

Droplet size oscillates periodically at intermediate shear rates.

Two steady states are identified: monodisperse droplets and shear-thinning transition.

Oscillations are driven by a balance between surface tension and viscous stress.

Abstract

Experimental observations of droplet size sustained oscillations are reported in a two-phase flow between a lamellar and a sponge phase. Under shear flow, this system presents two different steady states made of monodisperse multilamellar droplets, separated by a shear-thinning transition. At low and high shear rates, the droplet size results from a balance between surface tension and viscous stress whereas for intermediate shear rates, it becomes a periodic function of time. A possible mechanism for such kind of oscillations is discussed.