The impact of a flexible plate on a calm water surface: the effect of plate stiffness

The oblique impact of an elastic rectangular plate (length 108 cm, width 41 cm and thickness 0.66 cm) on a quiescent water surface is studied experimentally. The plate is installed via pinned supports to a dynamometer system, which is connected to a carriage capable of combined horizontal and vertical velocity components, U and V, respectively. The two short edges of the plate are held horizontal, while the angle between the plate's two long edges and the still water surface (called the pitch angle), U and V are varied. These variables are chosen to create a set of experimental conditions in which U/V is held constant while the dimensionless plate stiffness ratio (the ratio of the hydrodynamic pressure force to the plate length times its plate stiffness) is varied. It is found that at large pitch angles, the curves of dimensionless force and moment vs dimensionless time nearly collapse to a single curve, while at a small pitch angle, the curves are strongly affected by the stiffness ratio. This latter case indicates a strong fluid-structure interaction. Work on the effect of longitudinally varying plate stiffness ratio is also underway.