Study On The Effect Of Wave Group Interaction On The Distribution Of Wave Height

Research on the ocean wave group is important for ocean wave theory and ocean engineering. Research on ocean wave nonlinearity is an important realm of ocean wave study. The nonlinear wave-wave interactions are studied intensively. However, very few studies have been made on the influence of wave group interaction on the distribution of wave height.Results of many theoretical researches show that the evolvement of wave group envelope is controlled by nonlinear Schr(o|¨)dinger equation(NLS). In the case of two wave groups, the evolution of the envelope can be described by two coupled nonlinear Schr(o|¨)dinger equations (CNLS). This means that the interaction between wave group envelopes can be studied in the framework of CNLS.The wind wave field should be treated as superposition of many kinds of simple wave groups. The interaction of two wave groups is studied on the basis of CNLS. It is found that wave group interaction may cause the deviation of wave height distribution from the result of linear theory. For low and medium wave heights, in the case of nonlinearity the probability of exceedence is higher than the result of linearity. For waves with large height, in the case of nonlinearity the probability of exceedence is lower than the result of linearity. From average wave height to 1.5 times this height is the transition region. A parameter is introduced in studying the influence of wave group interaction on wave height distribution. It is a measure of the effect of nonlinearity on the distribution. The results show that for larger values of this parameter and for larger values of the average steepness, the deviation of the distribution from the result of linearity is largerThe result is in consistency with that of wind wave experiment. The parameter introduced in theory part corresponds to the ratio of right region area to left region area in a spectrum. It is a measure of the effect of nonlinearity on the distribution. For wind waves this parameter reflects the shape of the spectrum. The spectral shape is found to be an important factor in influencing the distribution of wave height. The results of wave height distribution for simulated waves show that the deviations of the wave height distribution of nonlinearity from linearity are caused by nonlinearity. The implication of these results is that the spectral shape is an important factor on the distribution of wave height and spectral shape parameters should be contained in the distribution in future studies.