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

Solvent exchange is a process involving mixing between a solute- containing good solvent and a poor one. The process creates oversaturation and thus the nucleation of the micro-sized solute droplets. Despite increasing interests and numerous efforts, such ternary systems on a macro-scale and in the turbulent regime have remained unexplored. We experimentally study the solvent exchange process by injecting mixtures of ethanol and trans-anethole into water, forming a turbulent buoyant jet with initial Reynolds numbers Re₀ = 555 and Re₀ = 1387, and two different compositions, namely ratios of ethanol:oil=100:1 and ethanol:oil=33:1, thus creating local oversaturation of the trans-anethole by turbulent entrainment. We measure the concentration of the nucleated droplets with a light attenuation technique and find the radial distribution to be sub-Gaussian. The evolution of the oversaturation flux reveals continuous droplet nucleation downstream and radially across the jet, in contrast to entrainment-based models, which we attribute to the limited mixing capacity of the jet. This work extends the understanding of solvent exchange into the turbulent regime for the first time, and brings in a novel type of flow, broadening the scope of multicomponent, multiphase turbulent jets with phase transition.