The effect of pitch angle on the oblique impact of a flexible plate on a water surface

The oblique impact of a flexible rectangular plate (length 108 cm, width 41 cm) on a water surface is studied experimentally. The plate is made of 6061 aluminum with a thickness of 6.61 mm and is mounted to a dynamometer through a pinned connection along each of the short edges. The undeformed plate is tilted with a nonzero pitch angle (α) relative to the still water surface while the two short edges remain horizontal and perpendicular to the motion trajectory of the plate. During the impact, the horizontal and vertical components of the plate velocity are kept constant between the passage of the two short edges through the still water level. Time resolved measurements of the impact force and moment, the under-plate spray root and the out-of-plane plate deflection are performed. By varying the impact velocity and the pitch angle, the effect of several parameters is explored. It is found that the effect of the normal impact velocity dominates at a single pitch angle over the given range of plate motion trajectories. With the same magnitude of the normal velocity, a smaller pitch angle results in a stronger impact, featured by greater impact force and stronger interaction between the fluid motion and the structural dynamics.