Oblique Water-Exit Dynamics of Neutrally Buoyant Spheroids

The water exit of submerged bodies is a fundamental free-surface problem relevant to trans-medium vehicles, underwater projectiles, and other ocean engineering applications. While previous studies have clarified many features of spherical-body water exit, it remains unclear how geometric anisotropy modifies the coupled translational, rotational, and lateral motions during oblique emergence. In this study, the oblique water exit of neutrally buoyant spheroids with different aspect ratios is investigated using a validated computational framework combining large-eddy simulation, volume-of-fluid free-surface capturing, and overset-mesh rigid-body motion. The spheroids are launched from a fixed depth with varying initial velocities and launch angles. The results show that aspect ratio has a limited influence on the overall velocity-loss trend but substantially alters the rotational response and trajectory deflection. Increasing aspect ratio strengthens the coupling between body attitude and trajectory evolution. Mechanism analysis shows that wake–interface interaction initiates both rotation and lateral deflection, whereas the Munk moment mainly amplifies an established rotational tendency. The image effect and free-surface deformation provide secondary contributions. These findings extend the physical understanding of oblique water exit from spherical to nonspherical bodies and provide insight into the motion and stability of geometrically anisotropic trans-medium bodies.