Experimental and numerical investigation of a freefall wedge vertically entering the water surface

Abstract

Experiments and numerical methods are developed to investigate the water entry of a freefall wedge with a focus on the evolution of the pressure on the impact sides (the side contacting water) and the top side (the dry side on the top of the wedge), evolution of the global hydrodynamic loads, evolution of the air-water interface, and wedge motion. It is found that a typical water entry of a freefall wedge can be divided into slamming, transition, collapse and post-closure stages. A single-fluid numerical model is presented to simulate the first three stages. The results are compared to experiments and good agreements are obtained. A two-fluid BEM is proposed to investigate the influence of the air flow before the closure of the cavity created on the top of the wedge. It is found that for the closure of the 2D cavity, the air flow starts to play an important role just before closure but due to the short duration, the influence of air flow on the body velocity and configuration of the air-water interface is limited.

Analysis of loads, motions and cavity dynamics during freefall wedges vertically entering the water surface

“…This is accordance with Wang et al´s experiments [1]. An approximate cavity evolution model is proposed.…”

“…The present study is focused on the kinematics and dynamics of the freefall wedge until the closure of the cavity. No consideration is given to the post-closure stage where air compressibility matters [1]. The time evolutions of the penetration depth, the velocity and the acceleration are analyzed and expressed explicitly.…”

“…When the root of the spray is far away from the knuckle, an open cavity is formed on the top of the wedge which then collapses. The collapse stage ends at closure (pinch-off) of the cavity during which the hydrodynamic loads change slowly [1]. The evolution of the global hydrodynamic loads, the wedge motions and the evolution of the cavity are of particular interest.…”

“…When a freefall wedge vertically enters the water surface, it may experience slamming, transition, collapse, and post-closure stages [1]. The slamming stage is the initial stage of the wedge penetrating the water surface.…”

“…Note that the numerical results presented in this paper are obtained by using the single-fluid BEM described in [1].…”