Hydrodynamics performance and dynamic analyses of a low-frequency broadband heaving WEC-type breakwater with customized tri-stable restoring force: A 2D numerical study

Abstract

Aiming to broaden the low-frequency operational bandwidth of an oscillating buoy wave energy converter-floating breakwater integrated system (OB WEC-FB), the double snap-through mechanism is utilized to change its linear response to a tri-stable one. The corresponding tri-stable restoring force-displacement curve are first designed to be adjustable based on the coordinates of equilibrium points. Then, the effects of equilibrium positions, spring stiffness, damping coefficient, and wave amplitude on the operational characteristics of a tri-stable floater are investigated in a two-dimensional fully-nonlinear numerical wave tank. The results show that a well-designed double snap-through mechanism can effectively lower the resonance frequency of floater and excite its large-amplitude inter-well oscillation under the action of low-frequency waves. The resulting tri-stable floater significantly outperforms its linear counterparts on both harvesting low-frequency wave energy and attenuating long waves. In addition, the underlying mechanism of coupling nonlinearity between the wave-structure interaction and nonlinear motion states is explored in detail. This paper indicates the potential of a customized tri-stable mechanism in simultaneously enhancing power absorption and wave attenuation at low frequencies and provides a valuable scheme for solving the problem of narrow operational bandwidth of OB WEC-FB.