Some asymptotic results in the theory of wave-energy devices (Q1062838)

\textit{D. V. Evans} has shown [J. Fluid Mech. 77, 1-25 (1976; Zbl 0346.76008)] how the solution of the radiation problem for water-waves gives all the necessary parameters for determining the efficiency of a wave-energy device. We consider how this radiation problem can be solved in certain limits for several types of device. First, a moving-cylinder device which is many wavelengths below the surface is examined, using \textit{F. G. Leppington} and \textit{P. F. Siew}'s method [Appl. Ocean Res. 2, 129-137 (1980)]. We then calculate the efficiency of a Cockerell raft device which is either many wavelengths, or only a small fraction of a wavelength, long. Finally, the problem of a thin, symmetric gas-filled bag in a wave field is solved and the first-order solution given for the efficiency.