Experimental investigation of the water entry and/or exit of axisymmetric bodies

This paper presents an experimental investigation of the evolution of the wetted surface and of the hydrodynamic force during the water exit of a body initially floating at the water surface, and during combined water entry and exit. The evolution of the surface of contact between the body and the water is measured using transparent mock-ups and an LED edge-lighting system. This technique makes it possible to follow the evolution of the wetted surface during both the entry and exit phases with a high-speed video camera placed above the mock-up. The feasibility of the technique is shown for different axisymmetric bodies: a circular disc, a cone and a sphere. The evolution of the hydrodynamic force and of the radius of the wetted surface measured during the experiments are compared with theoretical results obtained with a combined Wagner-modified von Karman approach (Tassin et al. J. Fluids Struct., vol. 40, 2013, pp. 317-336), the linearized water exit model of Korobkin et al. (J. Fluids Struct., vol. 69, 2017a, pp. 16-33) and the small-time self-similar solution of Korobkin et al. (J. Engng Maths, vol. 102, 2017b, pp. 117-130).