SOME CHARACTERISTICS OF BREAKING WAVES

Frederic Raichlen, Panos Papanicolaou

Abstract


In recent years there has been a surge in coastal engineering research devoted to various aspects of breaking waves including their kinematics at and after breaking. For a review of certain aspects of this field the interested reader is referred to Peregrine (1983) and Battjes (1988); in this discussion only certain publications pertinent to this investigation will be mentioned briefly. With the advent of laser-Doppler velocimetry (LDV) a number of investigators have measured the internal velocities of waves both before, at, and after breaking. For example, Nadaoka (1986) measured the velocities in the shoaling region under periodic breaking shallow water waves. This extensive study of the nearshore regions resulted in vector diagrams which described very well several spatial aspects of the flow shoreward of breaking. Skjelbreia (1987) also used LDV techniques to define the kinematic characteristics of breaking solitary waves. Measurements were made of the water particle velocities under spilling and plunging breaking waves both very near breaking and after breaking, close to the water surface and to the bottom. A high degree of reproducibility was possible with the laboratory wave generation system used so experiments were conducted at different locations with essentially the same wave; this will be discussed more fully later. Skjelbreia (1987) also presented vector diagrams of the velocities under plunging and spilling solitary breakers. These measurements when compared to those of Nadoaka (1986) raise several questions regarding similarities and differences between breaking oscillatory waves and waves of translation. In addition to detailed kinematic measurements, a macroscopic view of shoaling solitary waves was also taken by Skjelbreia (1987) yielding results on the variation of the wave height with distance both before and after breaking. Although there has been a considerable amount of work along these lines in the past, observations of the changes in the wave at and after breaking are still quite useful in developing an overall understanding of the breaking process.

Keywords


breaking waves; wave characteristics

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