Micro-droplet nucleation through solvent exchange in a turbulent buoyant jet

TL;DR

This study investigates solvent exchange in turbulent buoyant jets, revealing continuous droplet nucleation and concentration profiles, thus extending understanding of multicomponent multiphase turbulent flows with phase transitions.

Contribution

It provides the first experimental insights into solvent exchange dynamics in turbulent jets, highlighting continuous nucleation and non-Gaussian concentration profiles.

Findings

Radial concentration profile is sub-Gaussian.

Droplet nucleation occurs continuously downstream and across the jet.

Limited mixing capacity influences oversaturation and nucleation.

Abstract

Solvent exchange is a process involving mixing between a good solvent with dissolved solute and a poor solvent. The process creates local oversaturation which causes the nucleation of minute solute droplets. Such ternary systems on a macro-scale have remained unexplored in the turbulent regime. We experimentally study the solvent exchange process by injecting mixtures of ethanol and trans-anethole into water, forming a turbulent buoyant jet in upward direction. Locally, turbulent mixing causes oversaturation of the trans-anethole following turbulent entrainment. We optically measure the concentration of the nucleated droplets using a light attenuation technique and find that the radial concentration profile is sub-Gaussian. In contrast to the entrainment-based models, the spatial evolution of the oversaturation reveals continuous droplet nucleation downstream and radially across the jet, which we attribute to the limited mixing capacity of the jet. Though we are far from a full quantitative understanding, this work extends the knowledge on solvent exchange into the turbulent regime, and brings in a novel type of flow, broadening the scope of multicomponent, multiphase turbulent jets with phase transition.