Free Elastic Plate Impact into Water

Abstract The Wagner theory, developed 80 years ago, is an analytical method for solving problems where a body with small deadrise angle impacts onto an undisturbed water surface of infinite depth. In this study, two-dimensional impact models based on the Wagner theory are developed which account for the elasticity of the body, for large horizontal speed of the body and flow separation from the body. In chapter 3, the problems of inclined rigid and elastic plates, impacting the fluid vertically, are solved. The elastic plate deflection is governed by Euler’s beam equation, subject to free-free boundary conditions. In chapter 4 and 5, impact problems of rigid and elastic plates and blunt bodies with high horizontal speed are considered. A smooth separation of the free surface flow from the body is imposed by Kutta’s condition and the Brillouin-Villat condition. In chapter 6, we account for fluid separation from the body in the free vertical fall of a rigid plate and a blunt body. In all problems considered in this thesis, the rigid and elastic plate motions, the fluid flow, and the positions of the turnover regions and the separation points are coupled. We found that hydrodynamic forces on an elastic body can be significantly different from those on a rigid body. In particular, the elasticity of the body can promote cavitation and ventilation. It is shown that horizontal speed of the body increases the hydrodynamic forces on the body and the jet energy significantly. For free-fall problems at high horizontal speed, the body can exit the fluid after entering if the forward speed is large enough. It is illustrated that the hydrodynamic forces on the body and the motion of the body strongly depend on the separation model. For the Brillouin-Villat separation criterion, we found that the position of the separation point is sensitive to the body vibration.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of East Anglia

Year dc:date.issued

2013

Author dc:creator

• Reinhard, Moritz

Language dc:language

en