Partial Wave Damping in Pneumatic Breakwaters

Earlier experimental studies have shown that the power consumption in pneumatic (or hydraulic) breakwaters is very large if complete stopping of the oncoming waves is to be achieved. It is therefore of considerable interest to investigate quantitatively the partial damping achieved if the supplied power is insufficient to give complete wave stopping. The present paper is devoted to a theoretical analysis of this problem in the large-scale case. The characteristic feature of the large-scale breakwaters is that there may be a considerable amplitude amplification in the opposing current. The theory uses (1)The breakwater theory of Taylor published in 1955; (2)the condition about wave saturation in regions of strong opposing currents where local wave breaking occurs; and (3)the amplitude variation theory of Longuet-Higgins and Stewart issued in 1961. Reasonable agreement with the large-scale pneumatic experiment of Bulson of 1963 is obtained.