On the divergence of fluctuations at approaching catastrophic phase inversion in turbulent emulsions

Catastrophic phase inversion is the sudden and irreversible change in the morphology of emulsions after a slight increase in the volume fraction of the dispersed droplet phase. By combining experimental and numerical results, we show that, at approaching the critical volume fractions, emulsions display a divergence in fluctuations at the macroscopic scale and a characteristic change in droplets morphology at the smaller scales. At the macroscopic scale the fluctuations of the global torque are experimentally observed to diverge at approaching the critical volume fraction, indicating the presence of a dynamically varying and widely oscillating effective viscosity. At the same time, at the microscopic scale we observe the formation, and successive break-up, of larger and larger droplets. The work paves the way to connect micro- and macro-scales dynamics in turbulent emulsions and to develop a dynamics theory for the understanding of emulsion stability and catastrophic phase inversion.