This paper describes a numerical study of the hydrodynamics, pressure distribution, and attitude angle characteristics of spinning stones impacting a free surface. A numerical model is developed using the large-eddy simulation and volume-of-fluid techniques, and a wide range of cases are considered under different initial attack angles and spinning velocities. Three stages are defined according to the evolution of the vertical resultant force. For stones with a low spinning velocity and small attack angle, a high-pressure zone emerges at the bottom of the leading edge. Furthermore, the characteristics of the attack angle α and the roll angle φ are demonstrated and analyzed for different initial conditions. The results show that attack angle, roll angle, and vertical resultant force evolve differently for small attack angle compared with that for other initial attack angles, but a similar evolution law governs the attack angle and roll angle during the skipping process. Furthermore, the relations between amplitude and frequency of attitude angle oscillations and the initial attack angles and spinning velocities are presented.

This paper presents a comparative study on water entry and water walking events of elastic spheres using a fluid–structure interaction method. The sphere displacements, cavity formations, and hydrodynamic characteristics during the water entry and water walking events are investigated. When the impact angle decreases, an obliquely impacting elastic sphere on the water surface can undergo a transition from water entry events to water walking events. Based on the morphological classification of the cavity opening, the shapes of cavity openings formed by elastic spheres can be roughly predicted from material properties and impact conditions. Furthermore, the water walking event is characterized by three typical stages: impact below the surface, walking across the surface, and skipping from the surface. Each stage is analyzed in terms of sphere displacements and hydrodynamic characteristics. The results also show that the vertical hydrodynamic forces acting on elastic spheres are not always smaller than those acting on rigid spheres at all impact angles. The critical impact angle that results in an equivalent vertical hydrodynamic force acting on both elastic and rigid spheres can be predicted from the material properties and impact conditions of the elastic sphere.

The Arctic region is rich in energy resources and plays a critical role in global shipping. Consequently, countries worldwide prioritize the formulation of strategies for this region. Research on water entry has predominantly focused on water-only scenarios, with relatively little attention given to the more complex conditions involving floating ice. This study combines numerical simulations and experiments to investigate the ice-breaking water entry of slender bodies. The findings suggest that, during the water entry of a slender body, floating ice affects the diffusion and contraction of the liquid at the gas–liquid interface, which in turn influences air inflow and cavitation development. This alters the formation and evolution of the cavity. By inducing variations in cavity shape and altering cavity collapse time, the hydrodynamic and ballistic properties of the projectile are ultimately affected.

The importance of high-speed water entry is acknowledged within the defense industry. This study numerically investigates the water entry of a high-speed rectangle projectile, focusing on cavity dynamics and shock wave generation. A computational model is employed to accurately simulate the intricate fluid dynamics of compressible multiphase flows. This model integrates a dual-phase flow algorithm with a thermally sensitive Tait equation of state for the liquid phase. The primary focus lies in understanding the effects of fluid compressibility on cavity evolution and shock wave propagation across different Froude numbers. The findings reveal that compressibility induces changes in cavity formation size, leading to significant variations in phase composition within the cavity. Furthermore, compressibility enhances the air cushion effect upon surface impact, resulting in delayed water entry and concurrent reduction in projectile drag. Moreover, a prognostic model is proposed, correlating shock pressure with propagation distance, thereby validating theoretical hypotheses advanced by Lee et al. [J. Fluid Struct., 11, 819–844 (1997)].