Coagulation drives turbulence in binary fluid mixtures

TL;DR

This paper investigates how droplet coagulation induces turbulence in binary fluid mixtures, revealing a novel turbulence-driven coarsening mechanism with a specific growth law and self-similar structures.

Contribution

It uncovers a new turbulence-driven coarsening mechanism in binary fluids with distinct flow and droplet length scales, supported by simulations and scaling arguments.

Findings

Coagulation induces turbulence that drives domain growth.

The growth law follows t^{1/2} in the studied regime.

Self-similar structures are observed in flow and droplet configurations.

Abstract

We use direct numerical simulations and scaling arguments to study coarsening in binary fluid mixtures with a conserved order parameter in the droplet-spinodal regime -- the volume fraction of the droplets is neither too small nor symmetric -- for small diffusivity and viscosity. Coagulation of droplets drives a turbulent flow that eventually decays. We uncover a novel coarsening mechanism, driven by turbulence where the characteristic length scale of the flow is different from the characteristic length scale of droplets, giving rise to a domain growth law of $t^{1/2}$, where $t$ is time. At intermediate times, both the flow and the droplets form self-similar structures: the structure factor $S(q) \sim q^{-2}$ and the kinetic energy spectra $E(q) \sim q^{-5/3}$ for an intermediate range of $q$, the wavenumber.