Intermittent thermal convection in jammed emulsions

TL;DR

This paper investigates how heat transfer in jammed emulsions with yield-stress behavior occurs intermittently through bursts of convection, driven by fluidization and coalescence processes.

Contribution

It reveals the mechanism of intermittent convection in jammed emulsions and links it to droplet-scale dynamics and phase inversion phenomena.

Findings

Heat transfer occurs via intermittent convective bursts.

Fluidization and coalescence drive the convection process.

Emulsion phase inversion supports sustained convection.

Abstract

We study the process of thermal convection in jammed emulsions with a yield-stress rheology. We find that heat transfer occurs via an intermittent mechanism, whereby intense short-lived convective "heat bursts" are spaced out by long-lasting conductive periods. This behaviour is the result of a sequence of fluidization-rigidity transitions, rooted in a non-trivial interplay between emulsion yield-stress rheology and plastic activity, which we characterize via a statistical analysis of the dynamics at the droplet scale. We also show that droplets' coalescence induced during heat bursts leads to a spatially heterogeneous phase-inversion of the emulsion which eventually supports a sustained convective state.