Immiscible liquid jets are crucial in various physical and chemical processes. This study explores the dynamics of a buoyant immiscible liquid-in-liquid jet in the laminar regime using simultaneous particle image velocimetry and planar laser-induced fluorescence. A refractive index-matched fluid pair—silicone oil and a sugar water mixture—was employed to overcome optical distortions. Analytical solutions for both inviscid and viscous models were developed and compared with experimental data across a range of nondimensional parameters. The viscous model accurately predicts both the jet radius and centerline velocity, although some discrepancies appear in the continuous phase velocity distribution. Furthermore, experimental data reveal that boundary layer growth at the jet interface follows classical boundary layer scaling. The flow field was divided into two broad regions: a near-field region near the inlet and a far-field region several diameters away. Distinct scaling behaviors for the jet radius were observed in these two regions, guided by the relative significance of nondimensional parameters. Among these parameters, the buoyancy parameter, $N_j$, and the Reynolds number, $\text{Re}$, were found to play dominant roles in governing jet behavior. In contrast, the Weber number, $\text{We}$, was found to affect jet dynamics when its value was significantly lower than unity, while the viscosity of the continuous phase affected jet dynamics only in the far field.

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• Laminar flows
• Multiphase flows
• Wakes & jets