Berkeley Fluids Seminar
University of California, Berkeley
Bring your lunch and enjoy learning about fluids!
June 23, 2014
Dr. James Duncan (Mechanical Engineering, Maryland)
Exceptionally held at 12 noon in 3110 Etcheverry Hall
The Impact of Plunging Breaking Waves on a Partially Submerged Cube
The impact of a deep-water plunging breaking wave on a partially submerged cube is studied experimentally in a tank that is 14.8 m long and 1.2 m wide with a water depth of 0.91 m. The breakers are created from dispersively focused wave packets generated by a programmable wave maker. The water surface profile in the vertical center plane of the cube is measured using a cinematic laser-induced fluorescence technique with movie frame rates ranging from 300 to 4,500 Hz. The pressure distribution on the front face of the cube is measured with 24 fast-response sensors simultaneously with the wave profile measurements. The cube is positioned vertically at three heights relative to the mean water level and horizontally at a small range of positions along the tank. When the cube is half submerged and in the middle of this range of horizontal positions, the wave impact occurs without overturning of the water surface and a vertical water jet is formed on the front face of the cube. The portion of the water surface between the contact point on the front face of the cube and the wave crest is fitted with a circular arc and the radius and vertical position of the fitted circle are tracked during the impact. The vertical acceleration of the contact point reaches more than 30 times the acceleration of gravity and the pressure distribution just below the free surface shows a localized high-pressure region with a very high vertical gradient. For the cases when this jet is formed, the surface-shape history during the last moments before the jet forms becomes independent of the cube position.
This work is supported by the Office of Naval Research under grant N000141110095.