In a recent paper Chen and Saffman showed that periodic gravity waves in water of infinite depth are not unique. They presented explicit computations for new families of waves which they termed irregular waves. In the present paper the authors give conclusive numerical evidence that periodic gravity waves in water of arbitrary uniform depth are not unique. Explicit computations of irregular waves in water of finite depth are presented. In addition, they show that Chen and Saffman's bifurcation point for an irregular wave of class 2 is not unique. Results suggest the existence of an infinite number of such bifurcation points.
In this book linear and nonlinear theories of wave modification are considered. There are chapters focusing on linear wave scattering, nonlinear dispersive long waves and parabolic modelling, the interaction of waves with tidal and other currents, the trapping of wave energy in the vicinity of particular topographical features, and the mechanisms by which waves change the bed profile through sediment transport.
This book is a self-contained introduction to the theory of periodic, progressive, permanent waves on the surface of incompressible inviscid fluid. The problem of permanent water-waves has attracted a large number of physicists and mathematicians since Stokes' pioneering papers appeared in 1847 and 1880. Among many aspects of the problem, the authors focus on periodic progressive waves, which mean waves traveling at a constant speed with no change of shape. As a consequence, everything about standing waves are excluded and solitary waves are studied only partly. However, even for this restricted problem, quite a number of papers and books, in physics and mathematics, have appeared and more will continue to appear, showing the richness of the subject. In fact, there remain many open questions to be answered. The present book consists of two parts: numerical experiments and normal form analysis of the bifurcation equations. Prerequisite for reading it is an elementary knowledge of the Euler equations for incompressible inviscid fluid and of bifurcation theory. Readers are also expected to know functional analysis at an elementary level. Numerical experiments are reported so that any reader can re-examine the results with minimal labor: the methods used in this book are well-known and are described as clearly as possible. Thus, the reader with an elementary knowledge of numerical computation will have little difficulty in the re-examination.
This book presents two distinct aspects of wave dynamics – wave propagation and diffraction – with a focus on wave diffraction. The authors apply different mathematical methods to the solution of typical problems in the theory of wave propagation and diffraction and analyze the obtained results. The rigorous diffraction theory distinguishes three approaches: the method of surface currents, where the diffracted field is represented as a superposition of secondary spherical waves emitted by each element (the Huygens–Fresnel principle); the Fourier method; and the separation of variables and Wiener–Hopf transformation method. Chapter 1 presents mathematical methods related to studying the problems of wave diffraction theory, while Chapter 2 deals with spectral methods in the theory of wave propagation, focusing mainly on the Fourier methods to study the Stokes (gravity) waves on the surface of inviscid fluid. Chapter 3 then presents some results of modeling the refraction of surf ace gravity waves on the basis of the ray method, which originates from geometrical optics. Chapter 4 is devoted to the diffraction of surface gravity waves and the final two chapters discuss the diffraction of waves by semi-infinite domains on the basis of method of images and present some results on the problem of propagation of tsunami waves. Lastly, it provides insights into directions for further developing the wave diffraction theory.
Free surface flows arise in the natural world, physical and biological sciences and in some areas of modern technology and engineering. Exam ples include the breaking of sea waves on a harbour wall, the transport of sloshing fluids in partly filled containers, and the design of micronozzles for high speed ink-jet printing. Apart from the intrinsic mathematical challenge in describing and solving the governing equations, there are usually important environmental, safety and engineering features which need to be analysed and controlled. A rich variety of techniques has been developed over the past two decades to facilitate this analysis; singular perturbations, dynamical systems, and the development of sophisticated numerical codes. The extreme and sometimes violent nature of some free surface flows taxes these methods to the limit. The work presented at the symposium addressed these limits and can be loosely classified into four areas: (i) Axisymmetric free surface flows. There are a variety of problems in the printing, glass, fertiliser and fine chemical industries in which threads of fluid are made and controlled. Presentations were made in the areas of pinch-off for inviscid and viscous threads of fluid, recoil effects after droplet formation and the control of instability by forced vibration. (ii) Dynamic wetting. The motion of three phase contact lines, which are formed at the junction between two fluids and a solid, plays an important role in fluid mechanics.
