Numerical simulation investigation on water surface skipping motion characteristics of sea-skimming projectile

Water surface skipping is a kind of motion in which the bottom of the aircraft touches the water surface and bounces up repeatedly when it moves near the water surface. This motion can improve the unpowered range and maneuverability of the long-range projectile near the water surface. This paper uses the VOF method to capture the change in the water surface, the overset grid, and the equation of six degrees of freedom to simulate the rigid body motion in order to study the characteristics of projectile water surface skipping. This is done by solving the unsteady Navier-Stokes equation and the Realizable k-ε model. According to the change of projectile attitude and relative water surface position, the water surface skipping motion process of the projectile is divided into five stages. The process of the projectile sliding on the water surface is simulated. The findings indicate that there are five stages in the process of projectile water surface sliding: the air flight prior to contact with the water, the first water contact and bounce, the near-water surface gliding, the second water contact and sliding out of the water. These stages are based on changes in the projectile’s attitude and relative position to the water surface. The first time, the stern of the projectile touches the water and quickly bounces up from the water surface by the impact of the water surface, making the projectile pitch down. In this process, the projectile still moves toward the water surface. During the second water contact, the lower surface of the projectile slaps the water surface in a large area. The projectile is not only subjected to a large impact force on the water surface but also subjected to a nose-up moment. Under the lift impact force and the nose-up moment, the projectile glides out of the water surface. The combined effect of the lift torque generated by the stern of the projectile and the impact load generated at the water contact point of the projectile enables the projectile to complete the water surface skipping process.