Blunt-body impact on the free surface of a compressible liquid

Abstract

The present paper deals with the plane unsteady problem of the penetration of a blunt solid contour into an ideal compressible liquid. At the initial instant of time, the solid body touches the liquid free boundary at a single point. At the initial stage, the duration of which depends on the body geometry, the displacements of liquid particles are small and the disturbed fluid motion is described within the framework of the acoustic approximation. The main feature of the problem is the existence of a contact line between the free surface of the liquid and the solid-body surface. The position of this line is not known in advance and is to be determined together with the solution of the problem. A brief description of the method that provides a solution of complicated nonlinear problems such as this is given. The pressure distribution and the velocity field in the liquid are shown to be given in quadratures and in the case of a parabolic entering contour in an explicit form. For a parabolic entering contour the pressure at the top of the contour calculated using the model of an incompressible liquid is observed to deviate from a precise value by not more than 10% of the latter after the first expansion waves have passed the contact point. The solution analysis enabled us to distinguish the regions in which the acoustic approximation fails and the liquid flow becomes essentially nonlinear.

Experimental Study on Slamming Pressure and Hydroelastic Vibration of a Flat Plate during Water Entry

“…Environment, geometry, motion, mass, and structure stiffness are common factors that affect the impact load. Liquid compressibility and viscosity effects during the initial stage of water entry were discussed by Korobkin (1992Korobkin ( , 1994 and Iafrati and Korobkin (2004). An air cushion between plate and water surface was found by Chuang (1966) through a series of free falling tests.…”

Experimental and numerical study on hydrodynamic impact of a disk in pure and aerated water

“…Based on the acoustic framework, similar problems are further studied by other researchers like Poruchikov, 8 Asryan and Galin 9 and Korobkin. 10 Their study shows that the ignorance of the compressibility of water may lead to an overestimation of impact load. On the other hand, for water entry of a blunt body, the air between the free surface and structure may not be quick enough to escape, which results in a cushion during the impact.…”

Impact of two bodies one of which is covered by a thin layer of liquid

“…Therefore, under assumptions (i)-(vii) the equations of motion and the boundary conditions may be linearized, and the boundary conditions may be taken at the undisturbed liquid level in the first approximation. This idea was used by Korobkin (1994) for the first stage, by Wagner (1932) for the second, and by Galanin & Saikin (1 98 1) for the third stage. At the fourth stage the deformation of the liquid domain must be taken into account in any case.…”