Hydrodynamic force and attitude angle characteristics of a spinning stone impacting a free surface

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.