Water Entry of Cylindrical Shells: Theory and Experiments

Modeling hydroelastic response of lightweight structures to water impact plays a pivotal role in the design of lightweight marine vessels and crew capsules. In contrast to the majority of studies that focus on water entry of wedge-shaped bodies, this study addresses the hydroelastic impact of cylindrical shells. A cylindrical shape allows for a systematic study of the interplay between bending and stretching during water entry. This study puts forward a mathematically tractable framework to study the rigid body motion and elastic deformation of cylindrical shells, free falling onto a quiescent water surface. Donnel thin shell theory is used to model the shell, and Wagner theory is adopted to determine the hydrodynamic loading as a function of the rigid body motion and structural deformation. Galerkin method is employed to cast the problem into a manageable system of coupled ordinary differential equations, which are then solved numerically. Model predictions are validated against experiments on shells with two thicknesses, detailing both the flow physics and elastic response through the cogent integration of direct acceleration measurement, high-speed imaging, and particle image velocimetry. The proposed framework and experimental dataset are expected to constitute the foundations on which to formulate new theories for lightweight composites and testing computational schemes.