Initial Stage of Water Impact

Abstract

The problem of interaction between a solid body and a liquid with a free surface is a broad subject that includes several significant sections of classical and modern hydrodynamics. In this review we confine our dis­ cussion to processes characterized by strong unsteadiness in their develop­ ment and by the existence of a contact line between the free surface of the liquid and the solid-body surface. Detailed investigation of such processes can be applied to problems in ship building, aviation, and energetics (e.g. slamming problems, and the problems of the landing of flying boats and of high-velocity liquid-drop impact upon structural elements). In a general form, such processes can be described in the following manner: At the initial instant of time t = 0, a solid body touches a free surface of liquid. At this moment the position of the solid body, the domain occupied by the liquid, and the velocity field of the liquid particles are assumed to be known. For t > 0, either the law of body motion or the external forces affecting it are prescribed. The liquid flow and the character of its action upon the body.are to be determined. Interest in this field of hydrodynamics arose more than a half century ago in connection with the problem of the landing of flying boats. The first theories of solid-body impact with a liquid (the penetration theory of von Karm{m and the impact theory of Sedov) were directed at a global description of this process. Many applied problems have since been solved on the basis of these theories. But in some cases, more complete infor­ mation about the process is required. Thus, in studying material erosion it is important to know the stress distribution in the contact zone between the liquid and the solid-body surface. It is also necessary to take into account the peculiarities of the flow velocity field in order to determine the