Cavity dynamics and energy budget for composite-driven and jet-driven regimes in air-jet-assisted water entry

This study investigates the air-jet-assisted water entry and provides a numerical analysis of the experimentally observed composite-driven and jet-driven cavities. We employed numerical simulations to elucidate the differences in cavity propulsion, closure dynamics, and energy distribution during water entry. The results reveal that the closure of composite-driven cavities exhibits pronounced forced characteristics, arising from the abrupt transition between jet-driven and carrier-driven propulsion modes. In contrast, jet-driven cavities maintain stable propulsion for a significantly longer duration and close at greater depths. A dimensionless supply–demand ratio, combined with power-law fitting and velocity-based scaling parameters, demonstrates that the macroscopic closure processes of both cavity types are predominantly governed by a gravity–inertia mechanism, while the fitted exponent for the jet-driven case reveals a secondary, non-gravitational modification to the local self-similar scaling. Energy statistics further indicate that, in air-jet-assisted water entry, the overall energy partition is characterized by dominant dissipation, followed by boundary transport, with relatively limited energy storage. Jet-driven cavities exhibit a more uniform energy distribution compared to composite-driven ones.