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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 the 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 has a sub-Gaussian kurtosis. 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. Although 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.
