Droplet impact onto immiscible liquid pools is frequently observed in both natural and industrial processes. A detailed understanding of the interfacial dynamics and energy transfer mechanisms involved in such impacts is essential for advancing applications such as chemical synthesis, additive manufacturing, and pharmaceutical formulation. However, within the range of impact velocities relevant to these processes, the spatiotemporal evolution of the immiscible interface and the associated energy pathways remain insufficiently characterized. Previous models have predominantly attributed energy conversion to the formation of cavity potential energy, often neglecting other important components. In this study, we experimentally investigate the formation and evolution of cavities induced by millimeter-sized droplet impact on immiscible deep pools over a Froude number (Fr) range of ${10}^1–{10}^3$. Our results reveal that, in addition to cavity potential energy, cavity surface energy plays a nonnegligible role, and a substantial fraction of the droplet's initial kinetic energy is dissipated via viscous effects. To improve the accuracy of the cavity energy estimation, we introduce a shape factor $k$ to account for variations in cavity geometry under different impact conditions. We also propose a dissipation coefficient $\alpha$ that quantifies the relationship between viscous energy loss and the pool-droplet viscosity ratio. Based on the refined energy balance, we derive a dimensionless expression for the maximum cavity penetration depth. This model is semiempirical, with all variables retaining clear physical meaning. The findings offer new theoretical insights into the fluid dynamics of droplet impact on immiscible liquid interfaces.

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• Capillary interactions
• Cavitation
• Drop interactions
• Flow instability
• Interfacial flows
• Interfaces