Rigid-Body Water–Surface Impact Dynamics: Experiment and Semianalytical Approximation

Abstract

An experimental study of the dynamics of a generic rigid body during water impact and an equivalent-radius approximate analytical procedure is developed and calibrated in this study. The experimental tests in a wave basin covered a range of drop heights using a 1/6th-scale model of a practical water-landing object prototype for two drop mechanisms to determine the water impact and contact effects. The first mechanism involved a rope and pulley arrangement, while the second mechanism employed an electromagnetic release to drop the rigid body. Hydrodynamic parameters including peak acceleration and touchdown pressure were measured and the maximum impact/contact force was estimated for various entry speeds (corresponding to various drop heights) and weights of the rigid body. Results from the tests show that the impact acceleration and touchdown pressure increases approximately linearly with increasing drop height and the data provides conditions that keep impact accelerations under specified limits for the rigid-body prototype. The experimentally measured maximum accelerations were compared with classical von Karman and Wagner approximate closed-form solutions. In this study, an improved approximate solution procedure using an equivalent radius concept integrating experimental results with the von Karman and Wagner closed-form solutions is proposed and developed in detail. The resulting semianalytical estimates are calibrated against experimental results and found to provide close matching.