Numerical Modeling Of Nonlinear Irregular Wave Transform In Shallow Water.

A combined refraction-diffraction mathematical model of irregular wave propagation and analytic algorithms of the simulation spectrum and its parameters by the means of discrete spectrum are established in this paper, which are based on nonlinear model of wave propagation for slowly varying depth, water level and current field. At the same time, the propagation and transformation of three wave types are modeled by three modes: refraction theory mode, linear mode and nonlinear mode, the types of wave including directional spectrum, 1-D frequency spectrum and regular wave characterized by significant wave height and mean wave period. Meanwhile, 2-D spectrum and the corresponding parameters of irregular wave transformation (predominant wave direction and mean wave direction, peak frequency and peak spectrum density, spectrum width, mean period, mean wave length, mean wave crest length and 3-D index and so on), 1-D frequency spectrum and the corresponding parameters and numerical results of wave height, wave direction of regular wave transformation are offered.In this paper, three methods are carried out to calculate and comparative analyze the mean wave direction, the same as mean wave length with four methods. According to systematic comparative analyses, it is showed that modeling results present evident difference due to different numerical model and different type of wave, especially in the area which the relative depth is shallow. In addition, the error of pure refraction model is bigger, which indicates that it is very necessary to research wave propagation with irregular method.