NUMERICAL-SIMULATION OF IRREGULAR WAVE-PROPAGATION OVER SHOAL

While studying the bathymetric transformation of ocean waves propagating into a coastal region, the engineer often invokes the concept of the significant wave to represent the offshore irregular sea state. As an approximation, the propagation characteristics of a regular wave train (with properties equal to that of the significant wave) are determined, instead of those of the actual irregular sea state. However, recent experimental investigations by Vincent and Briggs have shown that for the case of combined refraction-diffraction of waves by a shoal, the propagation characteristics of the irregular and equivalent regular (monochromatic) wave conditions can be vastly different. At the same time, researchers are investing substantial effort in the construction of accurate numerical refractiondiffraction models for monochromatic waves. Although the monochromatic representation gives a poor approximation of the spectral conditions, this study shows that a monochromatic refraction-diffraction model can be used to make spectral calculations that agree closely with the actual irregular conditions observed in a hydraulic model. Further, these calculations can also help explain all the observed differences in the propagation of regular and various types of spectral conditions over the shoal. ASCE.

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