Numerical Investigation of Wave Energy Absorbed by the Edinburgh Nodding Duck Device in Front of a Vertical Wall

Abstract

Abstract An open-source computational fluid dynamics (CFD) package, openfoam, is extended and applied to study the power takeoff (PTO) efficiency absorbed by an Edinburgh nodding duck wave energy converter (WEC) device installed in front of a vertical wall. The duck WEC device is axis-fixed by a rigid cantilever beam extended from the vertical wall. After numerical validations and convergent verifications, the characteristics of the duck WEC device for power takeoff with various distances between the rotation center of the duck WEC device and the vertical wall are examined. The present numerical investigation illustrates that the absorbing efficiency by the duck WEC device is insensitive to the distance when subjected to incident waves of higher frequencies, while sensitive when subjected to incident waves of lower frequencies. Furthermore, for incident waves of lower frequencies, when the distance is approximately 0.58 times of the wavelength, a lower absorbing efficiency is achieved. While a higher absorbing efficiency is achieved, when the distance is approximately 0.32 times of the wavelength. Besides, the wave-induced force and torque impacting on the vertical wall are checked. It is found that both the force and torque significantly decrease when the distance is approximately 0.32 times of the wavelength, owing to the installation of the duck WEC device in front of the vertical wall.