The Oblique Impact of a Flexible Flat Plate on a Water Surface*

The impact of a flexible aluminum plate (122 cm by 38 cm by 0.79 cm) on a quiescent water surface is studied experimentally. The plate is installed with a roll angle of 10° and a pitch angle of 5° and approaches the water surface with three sets of horizontal (U) and vertical (W) velocity components, (U, W) = (5.0, 1.0), (4.0, 0.8), (3.0, 0.6) m/s. The surface profiles of the spray generated during the impact are measured with a laser induced fluorescence technique in a vertical plane perpendicular to the horizontal motion. The deformation of the plate is characterized by strain and out-of-plane deflection measurements at various locations on the top surface of the plate. The strains are measured with novel optical fiber Bragg grating sensors. Two types of spray are found and their behaviors vary significantly with impact speed. The location of maximum strain propagates from the trailing edge to the leading edge of the plate. The maximum deflection at the middle of the plate increases linearly with the impact speed. The spray measurements are compared to those from companion experiments with a rigid plate.