ORIGIN, EFFECT AND SUPPRESSION OF SECONDARY WAVES

C.H. Hulsbergen

Abstract


Beach profile formation may be severely affected by secondary waves which, together with the basic wave, always originate from a sinusoidally.moving wave board The ascertainment of this experimental fact is followed by an investigation of the behaviour of the generated waves and their interactions It appears that the many characteristic features, among which the spatial beat phenomenon and the secondary crest formation, are generally in good accordance with the theories of Fontanet [I4j, and Kravtchenko and Santon I 20J It is concluded that an "outer" analysis, eg by plotting the x-tlines of visible peaks, is only of limited use to describe the "inner" character of the complex phenomenon. The subsequent study of the effect of secondary waves on a horizontal sand bed reveals that not only the wave form, but also the sand transport varies spatially, resulting in the formation of bars and troughs This typical behaviour of the onshore-offshore transport is provisionally investigated in a small pulsating water block. Finally, a method is described which suppresses the secondary waves, by using a low rectangular sill on the otherwise horizontal bottom.

Keywords


secondary waves; wave origin; wave suppression

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