Numerical analysis of turbulence evolution and flow dynamics due to spherical body water entry: Effects of mass and drop height

The hydrodynamic interactions during water entry are critical for the design of unmanned aerial vehicles (UAVs) and autonomous underwater vehicles (AUVs) operating in challenging environments. This study investigates the flow dynamics and turbulence characteristics induced by spherical bodies of varying mass impacting still water from different heights. A two-dimensional numerical framework employing the Arbitrary Lagrangian-Eulerian (ALE) approach with adaptive remeshing was used to simulate the multiphase flow during water entry. The numerical model was validated against experimental data for radial velocity profiles. Key flow parameters, including pressure distribution, normalized radial velocity, turbulent kinetic energy, and turbulent dissipation rate, were analyzed as functions of radial distance from the sphere. Spectral analysis of surface elevation and radial velocity signals revealed that increasing sphere mass led to steeper power spectral density (PSD) slopes at lower fall heights, indicating enhanced low-frequency flow activity. Conversely, higher drop heights resulted in flatter PSD slopes, suggesting a broader distribution of flow energy across frequencies. The insights gained from this study contribute to an improved understanding of impact-driven flow dynamics in multiphase systems, with applications in the design and optimization of water-entry vehicles and devices.