Wave Attenuation by Porous Walled Breakwater

by Eugene P. Richey, (M.ASCE), Prof.; Dept. of Civ. Engrg., Univ. of Washington, Seattle, WA,
Charles K. Sollitt, Grad. Student; Massachusetts Inst. of Technol., Cambridge, MA,

Serial Information: Journal of the Waterways, Harbors and Coastal Engineering Division, 1970, Vol. 96, Issue 3, Pg. 643-663

Document Type: Journal Paper

Discussion: Black Jared L. (See full record)

Abstract: One method proposed for minimizing the energy content of wind waves reflected from a floating bridge incorporates an L-shaped chamber as a structural part of the bridge. The basic chamber has a vertical leg perforated with circular holes, the bottom is solid. A linearized differential equation describing the hydraulics of the system has the form of a forced, damped oscillator; here, the term analogous to the natural frequency contains the key dimensions of the breakwater and an added mass term. Solutions show the quantitative dependence of reflection coefficient upon the ratio of wave frequency to system (natural) frequency, wave camber, wall porosity, and chamber dimensions. The breakwater is most efficient (reflection coefficient as low as 0.2) when the frequency of the incident wave is near the system frequency, which provides a design link between incident wave and optimum breakwater dimensions. A prototype design example is included.

Subject Headings: Wave reflection | Breakwaters | Frequency response | Wind power | Wind waves | Bridges | Wave attenuation |

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