Dynamics of a neutrally buoyant sphere during oblique water exit

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Huang, Yang and Xiao, Qing and Zhu, Qiang (2025) Dynamics of a neutrally buoyant sphere during oblique water exit. Physical Review Fluids, 10 (12). 124805. ISSN 2469-990X (https://doi.org/10.1103/xj4j-jtkl)

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Abstract

Understanding the water exit dynamics of solid bodies is of fundamental importance for trans-medium vehicles, projectiles, and other ocean engineering applications. The water exit of a neutrally buoyant sphere is investigated using large-eddy simulation combined with an overset mesh technique. The sphere is launched from a fixed depth with varying initial velocities and launch angles. The results reveal distinct features of velocity attenuation, rotational response, and trajectory deflection. The critical exit velocity exhibits a nonlinear dependence on the launch angle (0). The exit process consists of two stages: in the fully submerged phase, the relative velocity loss decreases with increasing initial velocity, whereas in the partially submerged phase, the loss approaches a 0-dependent constant. The sphere undergoes rotation whose magnitude converges to a 0-dependent limit, with the rotation direction switching from clockwise to counterclockwise as 0 increases. Lateral trajectory deflection occurs in most cases, except at 0 = 0° and 45°, and is primarily governed by the interaction between the shed vortices and the free surface together with the image effect. Secondary contributions, including the sphere’s rotation and asymmetric wave-induced pressure distribution, amplify the deflection magnitude but do not alter its direction. These findings provide new physical insight into the mechanisms of water exit and underscore the critical role of launch conditions, with implications for predicting and controlling the motion and stability of underwater vehicles, projectiles, and marine structures.

ORCID iDs

Huang, Yang ORCID logoORCID: https://orcid.org/0000-0003-3581-2351, Xiao, Qing ORCID logoORCID: https://orcid.org/0000-0001-8512-5299 and Zhu, Qiang;
CORE (COnnecting REpositories)