Connecting the Drops: Observing Collective Flow Behavior in Emulsions

Abstract

Thoroughly mixing immiscible fluids creates droplets of one phase dispersed in a continuum of the other phase. In such emulsions, the individual droplets have rather mundane mechanical behavior. However, densely confining these suspended droplets generates a packing of particles with a spectacular diversity of mechanical behavior whose origins we are only beginning to understand. This mini review serves to survey a non-exhaustive range of experimental dense slow flow emulsion work. To embed these works in the context of the flow behavior of other structured fluids, we also discuss briefly the related non-local flow modeling attempts as one of the approaches that has been used successfully in describing emulsion flow properties and other materials.

Quantifying cooperative flow of fat crystal dispersions

“…5 As a result, the flowing material is macroscopically fluidized and, thus, exhibits higher velocities and larger spatial heterogeneities of viscosity as compared to theoretical predictions in the absence of cooperativity. Despite many experimental and numerical studies conducted over the last two decades, 6,7 a quantitative and comprehensive characterization of flow cooperativity is still missing, specifically regarding its dependence on microstructural and confinement properties. Thus, predicting cooperativity effects in fundamental soft matter studies, and in industrial applications of complex fluids, remains an open challenge.…”

“…Despite many experimental and numerical studies conducted over the last two decades, 6,7 a quantitative and comprehensive characterization of flow cooperativity is still missing, specifically regarding its dependence on microstructural and confinement properties. Thus, predicting cooperativity effects in fundamental soft matter studies, and in industrial applications of complex fluids, remains an open challenge.…”

Lagrangian statistics of concentrated emulsions

“…Understanding the dynamics of concentrated suspensions of soft, athermal particles such as emulsions, foams or gels is key to many natural and industrial processes (Larson 1999;Coussot 2005;McClements 2015). A central question concerns the connection between mechanisms occurring at the microstructure level and the macroscopic flow and rheological properties in these systems (Cohen-Addad, Hohler & Pitois 2013; Dollet & Christophe 2014;Bonn et al 2017;Dijksman 2019). For instance, irreversible topological rearrangements, corresponding to local yielding events, are known to be directly related to the inhomogeneous fluidisation of soft glassy materials (Goyon et al 2008;Bocquet, Colin & Ajdari 2009;Bouzid et al 2015;Dollet, Scagliarini & Sbragaglia 2015;Fei et al 2020).…”

“…A central question concerns the connection between mechanisms occurring at the microstructure level and the macroscopic flow and rheological properties in these systems (Cohen-Addad, Hohler & Pitois 2013; Dollet & Christophe 2014; Bonn et al. 2017; Dijksman 2019). For instance, irreversible topological rearrangements, corresponding to local yielding events, are known to be directly related to the inhomogeneous fluidisation of soft glassy materials (Goyon et al.…”