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Mathematical Problems in Engineering
Volume 2018, Article ID 1710253, 15 pages
https://doi.org/10.1155/2018/1710253
Research Article

Mathematical Framework for Hydromechanical Time-Domain Simulation of Wave Energy Converters

1Massachusetts Institute of Technology, 77 Massachusetts Avenue, Room 5-423, Cambridge, MA 02139, USA
2Virginia Tech, Randolph Hall, RM 332-4, 460 Old Turner St., Blacksburg, VA 24061, USA

Correspondence should be addressed to J. Seixas de Medeiros; ude.tim@msoaoj

Received 1 September 2017; Accepted 7 December 2017; Published 17 January 2018

Academic Editor: Renata Archetti

Copyright © 2018 J. Seixas de Medeiros and S. Brizzolara. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Efficient design of wave energy converters based on floating body motion heavily depends on the capacity of the designer to accurately predict the device’s dynamics, which ultimately leads to the power extraction. We present a (quasi-nonlinear) time-domain hydromechanical dynamic model to simulate a particular type of pitch-resonant WEC which uses gyroscopes for power extraction. The dynamic model consists of a time-domain three-dimensional Rankine panel method coupled, during time integration, with a MATLAB algorithm that solves for the equations of the gyroscope and Power Take-Off (PTO). The former acts as a force block, calculating the forces due to the waves on the hull, which is then sent to the latter through TCP/IP, which couples the external dynamics and performs the time integration using a 4th-order Runge-Kutta method. The panel method, accounting for the gyroscope and PTO dynamics, is then used for the calculation of the optimal flywheel spin, PTO damping, and average power extracted, completing the basic design cycle of the WEC. The proposed numerical method framework is capable of considering virtually any type of nonlinear force (e.g., nonlinear wave loads) and it is applied and verified in the paper against the traditional frequency domain linear model. It proved to be a versatile tool to verify performance in resonant conditions.