The Oscillating Water Column Wave-energy Device

An expression is obtained for the efficiency of wave-energy absorption of a float connected to a spring-dashpot system on the top of a column of fluid bounded by two closely-spaced vertical parallel plates or a narrow tube immersed under waves. The method makes extensive use of the approximate solution using matched asymptotic expansions obtained by Newman (1974) to the corresponding problem when the float-spring-dashpot system was absent. It is shown that for plates of equal length the maximum possible efficiency is 50%, and that for the three-dimensional case it is theoretically possible to capture the energy in a wave whose crest length is greater than the tube diameter.