Divergence of critical fluctuations on approaching catastrophic phase inversion in turbulent emulsions

TL;DR

This study investigates the critical fluctuations and dynamics leading to catastrophic phase inversion in turbulent emulsions, revealing divergence in torque fluctuations and the role of droplet heterogeneity, advancing understanding of this complex phase transition.

Contribution

It provides the first detailed experimental and numerical analysis linking torque fluctuation divergence to droplet heterogeneity during phase inversion.

Findings

Torque fluctuations diverge as a power-law near the critical volume fraction.

Heterogeneous droplet structures form and grow as inversion approaches.

Hysteresis observed in torque and droplet size across the inversion point.

Abstract

Catastrophic phase inversion, the sudden breakdown of a dense emulsion, occurs when the dispersed majority phase irreversibly exchanges role with the continuous minority phase. This common process has been extensively studied over the past decades and yet its fundamental physical mechanism has remained largely unexplored. Here we experimentally and numerically study the dynamics of catastrophic phase inversion as it occurs when the volume fraction of the dispersed phase exceeds a critical volume fraction (typically around 92% in experiments). Our data accurately quantify the abrupt change of both the global torque and average droplet size at approaching and across the phase inversion point, exhibiting strong hysteresis. Most importantly, we reveal that the fluctuations in the global torque diverge as a power-law while approaching the critical volume-fraction and we connect their growth to the formation of highly heterogeneous spatial droplet structures. The present finding, unveiling the tight connection between fluctuations in dynamic heterogeneity and the critical divergence of torque fluctuation, paves the way to a quantitative description of catastrophic phase inversion as an out-of-equilibrium critical-like phenomena.