Solvent exchange near turbulent/non-turbulent interface in a quasi-two-dimensional turbulent jet*

The scalar profiles induced by solvent exchange near the turbulent/non-turbulent interface (TNTI) are investigated in a quasi-2D turbulent jet. We inject mixtures of ethanol and anise oil upward into water with Re₀ between 500 and 800. The nucleation of the oil droplets, also known as ouzo effect, follows the entrainment and mixing with ambient water. Using a light attenuation technique, we measure the scalar field near the TNTI at two axial positions. At the upstream location, the mean concentration variation with height suggests that nucleation is competing with dilution. Conditioning on the distance to the TNTI, the ouzo scalar exhibits a sharp gradient as the passive scalar. However, nucleation alters the distribution in the turbulent region, leading to distinct profiles. The probability density functions (p.d.f.) reveal the increasing source term toward the turbulent core, and the bimodal distribution near the TNTI signals non-uniform mixing and potentially the effect of both nucleation and dissolution. At the downstream spot, while the source term is less visible, the p.d.f.s near TNTI are also bimodal, suggesting pronounced dissolution. This study unveils the interplay among mixing, nucleation, and dissolution in a quasi-2D turbulent jet with solvent exchange.