This book is intended to provide a thorough consideration of the interaction between waves and oscillating systems (immersed bodies and “oscillating water columns”) under conditions where amplitudes are sufficiently small that linear theory is applicable. In practice, this small-wave assumption is reasonably valid for most of the time, during which, for example, a wave-energy converter is generating most of its income. During the rather rare extreme-wave situations, however, non-linear effects may be significant, and such situations influence design loads, and hence the costs, for ships and other installations deployed at sea. This matter is treated in several other books.

The present book is mainly based on lecture notes from a postgraduate university course on water waves and extraction of energy from ocean waves, which I have taught many times since 1979. For the purposes of this book, I have selected those parts of the subject which have more general interest, rather than those parts of my course which pertain to wave-power conversion in particular. I hope that the book is thus of interest to a much wider readership than just the wave-energy community.

Except in 1983, my course has been taught every second year, mainly for doctorate students at the university in Trondheim, but other interested students have also attended. Moreover, a similar two-week course was given in 1986 with participants from Norwegian industry. Another two-week course, with international participation, was held at the Chalmers University of Technology in Gothenburg, Sweden, in 1998.

In February 1980, the lecture notes were issued in a bound volume entitled Hydrodynamisk teori for bølgjekraftverk (“Hydrodynamic theory for wave power plants”) by L. C. Iversen and me.