Sheng, Wanan and Aggidis, George
(2022)
*Fundamentals of Wave Energy Conversions : The Dynamics of the wave-structure interaction and wave energy optimisation.*
Eliva Press.
ISBN 9789994983769

## Abstract

This book is largely a summary of our research work on wave energy conversion in the past 20 years or so. In fact, the research work and the revenant publications have formed the main components in some chapters in this book. In addition, to make the book complete, our understandings on the principles to both hydrodynamics and aerodynamics, as well as the fundamental fluid dynamics, are also included, which are mainly based on our research experiences back to past 35 years (the 1st author’s). This book is targeting for providing the fundamentals on wave-structure interaction and further on the wave energy conversions, with some practical examples for those who are interested in wave-structure interactions (including wave energy conversions), as well as those who want to enhance their understandings on the issues. This book can be also used for other purposes, for instance, the first 8 chapters provide the fundamental contents for the studies on potential flows, and on wave-structure interactions for all marine platforms, such as the offshore wind energy platforms and other ocean platforms. The book consists of 13 chapters, and each chapter targets on different topic and issues. These include: Chapter 1: Introduction The brief introduction of wave energy resources and the wave energy technology principle and classifications. Chapter 2: Fluid-Structure Interaction The fundamentals of fluid dynamics, including Navier-Stokes equation and Euler equation, as well as the general solution of the Euler equation for the steady inviscid flows, the Bernoulli’s equation. Details are also given on how the fluid and structure interact. Chapter 3: Potential Flow Theory- Fundamentals Discussions on the relation between the inviscid flow and the potential flow, and why we can apply potential flows and how the fluid dynamics problems can be simplified, with the basic equation and understandings for potential flows. Chapter 4: Wave Theory and Wave Energy The introduction on how we can use potential flow to solve the linear waves, which is the most applied wave theory over a large range of applications, together with the calculation of wave energy. Then wave transformations are discussed when they travel to shallow waters and constraint areas. In addition, the nonlinear wave theory, such as the 2nd and 3rd Stokes waves, have also been briefly introduced. Chapter 5: Wind-Generated Waves & Wave Climates The method to describe the ocean random waves (irregular waves), with the details on how to calculate the relevant statistical parameters so for representing the wave states. Further discussions are on the wave climate and the forecasting of the wave extremes. Chapter 6: Potential Flow Theory & Fluid-Structure Interactions Fundamentals of the potential flow theory on the fluid-structure interaction, providing the basic theory and mathematical equations on how the general potential flow and structure interact, for instance, how the general structure can be expressed in terms of potential functions. Chapter 7: Potential Flow Theory & Wave-Structure Interaction The specific theory and application of potential flow-structure interactions in wave-structure interaction, on the principle and the mathematical equations for solving the problems of free surface, as well as the potential decomposition method, the diffraction and radiation potential functions for wave-structure interactions. Chapter 8: Potential Flow Theory & Panel Method for Wave-Structure Interactions The discussions on solving the potential flow theory for wave-structure interaction using the numerical scheme: panel methods, and the introduction of the panel method software packages, including both commercials and open sources. Chapter 9: Power Take-offs & Wave Energy Conversion (with examples of wave energy conversions) This chapter discusses the mathematical equations with power take-off (PTO) for wave energy conversion (into more useful mechanical energy) in frequency domain analysis (only for linear dynamic systems), including point absorber and oscillating water column wave energy converters, both in bottom-referenced form (bottom fixed devices) or self-referenced form (floating devices). Chapter 10: Optimisations of Power Take-off (for Improving Wave Energy Conversions) The methods on how the PTO can be optimised such that the possible maximisation of wave energy extraction can be achieved. Again these are for both point absorber and oscillating water column wave energy converters. Chapter 11: Wave Energy Conversion: Time-Domain Analyses The discussions on the transformation from the frequency-domain equation and analyses to the time-domain equation and analyses. This is a pre-requisite if the nonlinear effects, including the nonlinear PTO and the practical control technologies, are in considerations in the practical problems. Chapter 12: Control Technologies for Improving Wave Energy Conversion The detailed discussions on PTO optimisation and how these principles can be applied in the PTO control technologies for improving wave energy extraction. And to make control technologies in a more clear and compact form, the technologies are classified into three types: resistive loading/control; on-off control and reactive control, based on mainly on how much the optimisation conditions can be realised. Accordingly, the relevant descriptions and discussions have been made for each control category. In this chapter, we have paid our especial attention on the reactive controls, providing a collective and complete derivation for the model predictive control (MPC). Chapter 13: Dimensional Analysis and Physical Modelling of Wave Energy Converters An introduction why and how a down-scaled physical modelling of a marine structure can be carried out in wave tanks and what are the criteria for the physical modelling, together with the issues on how we can model the PTO system in the model scale.