Conceptual hydrodynamics of 2 dimensional lift-based wave energy converters

Most wave energy converters seek to exploit either the buoyancy (Froude-Krylov) and/or diffraction force regimes, coupling with either the wave-induced fluid particle displacement and/or acceleration respectively. Comparatively few designs have been proposed that couple with the wave-induced fluid particle velocity to generate an excitation force based on hydrodynamic lift. Furthermore, there is relatively little academic literature focused on, and thus a reduced understanding of, the fundamental hydrodynamics of such systems. Consequently, this paper provides a foundation for the development of that fundamental knowledge. Using a phenomenological approach, this paper develops a far field mathematical framework suitable for investigating the hydrodynamic characteristics of 2D lift-based wave energy converters. An analytical expression is developed for the maximum possible power capture of a rotational lift-based wave energy converter and it is shown that 100% power capture is possible. Analytical expressions are developed that provide the device characteristics required to achieve maximum power capture. Furthermore, it is shown that maximising the driving lift force generated does not maximise power capture. Rather, there is a specific finite magnitude of lift force required to achieve peak performance, meaning that if the driving lift force is increased beyond this point, power capture will be reduced.