Experimental study on cavity evolution and motion stability during oblique water entry of high-speed objects

Understanding the dynamics of oblique water entry is essential for enhancing the stability, control, and design of high-speed underwater objects and vehicles in engineering and defense applications. This study investigates the cavity profile evolution and trajectory stability through controlled experiments using a high-pressure light-gas launcher and high-speed imaging. Model bodies with varying slenderness ratios, cavitator diameters, materials, and entry angles were tested. Entry velocity was determined from image-tracked trajectories. Results show that lower slenderness ratios increase susceptibility to tail-slap and reduce trajectory stability. Smaller entry angles intensify cavity wall vaporization, delay cavity separation, and result in deeper closure depths. Larger cavitator diameters enhance stability, with cavity collapse primarily caused by re-entrant jets. Objects with greater momentum exhibited more gradual velocity decay, while those with lower density decelerated more rapidly. These findings offer valuable guidance for the design and predictive modeling of high-speed water-entry bodies.