Effects of wave conditions on the impact loads and stability of a high-speed projectile during oblique water entry

Understanding the water entry in waves is crucial for the structural safety and stability of vehicles. This study numerically investigates the dynamics of the high-speed water entry of a slender, truncated-cone-shaped projectile under varying wave conditions. The numerical model employs the Reynolds-averaged Navier–Stokes method with an overlapping grid. The focus is put on the influence of the wave phases, speeds, and entry angles on the motion trajectory and associated flow field evolution. Wave presence significantly affects cavity formation compared with static water, with pronounced asymmetry observed during vertical water entry at zero-crossing points, leading to asymmetric hydrodynamic forces and pitch deviations. Substantial transient radial forces are generated, raising concerns regarding the structural integrity under adverse sea conditions. At wave crests or troughs, increased wave forces result in higher peak drag forces, particularly during the crest entry. The entry angle significantly influences hydrodynamic performance. A larger entry angle generally increases the drag and alters the lift, thereby affecting the stability and trajectory of the projectile. As the entry angle increased, a greater asymmetry between the left and right cavities appeared, particularly at 25°, where the left cavity was smaller. Moreover, higher entry angles often resulted in increased surface splashing and spray generation. This can affect the aerodynamic characteristics of the projectile and lead to additional drag forces that should be considered in the design. The results can help understand the dynamic loads of vehicles under wave conditions, thereby enhancing their trajectory stability and optimizing the structural design.