The Impact of a Flexible Plate on a Wavy Surface*

The oblique impact of rectangular aluminum plates (length 108 cm and width 41 cm) on a wavy water surface are studied experimentally as a prototypical geometry for better understanding the strong nonlinear coupling of elastic objects as they impact a fluid domain. The plates are mounted at an angle inclined 10 degrees above the still water surface (leading edge up) via a 6-component dynamometer frame to a translational carriage capable of both horizontal and vertical motion. Previous experiments were performed with plates impacting a quiescent water surface while varying the impact kinematics, effective plate stiffness, and impact time scales. It was found that the loading and deformation was controlled by the plate's local inclination angle at the instantaneous position of the spray root where the plate intersects the water surface. In the present experiments, oblique impacts on a wavy surface are explored during which a large portion of the plate surface is nearly parallel to a section of the dynamically moving water surface. The wavy surface consists of a single frequency sinusoidal wave train with wavelengths on the order of the plate length. The direction of wave travel is opposite to the direction of the plate's horizontal motion. The plate kinematics, wave height, and impact location along the wavelength are varied.