On the Spray Generated during the Vertical Impact of a Rigid Flat Plate on a Quiescent Water Surface

The spray generated as a rigid rectangular plate (122 cm by 38 cm) is driven with a controlled motion into a quiescent water surface is studied experimentally. The plate is oriented with its long edges horizontal and its short edges set at various angles between 10 and 25 degrees from horizontal. The velocity of the plate (W) remains constant (0.4 ≤ W ≤ 1.2 m/s) from initial impact until the upper long edge of the plate reaches the mean water level. A laser induced fluorescence technique is used to measure the evolution of the spray in a vertical plane at the center of the long edges of the plate. As the plate's lower edge reaches the water surface, a thin jet (defined as Type I spray) is generated and moves along the bottom surface of the plate at high speed. This jet connects to the rising water surface under the plate via a root point and breaks up into ligaments and droplets at its tip. As the root point reaches the horizontal position of the upper edge of the plate, a thin spray sheet (Type II spray) begins to form from the surrounding water surface. Various characteristics of both sprays are explored in detail.