The Study On Developing Model Of The Wind Wave Spectrum

At present, wind wave spectrum has been studied extensively, for its important effect on theory study and practicality. But, from now on, the method that obtains the wind wave spectrum by the theory has not been got, because of the complexity of the objectivity. So the method that has been adopted frequently is as follow: first of all, we assume that the wave can be described by the existing spectrum, and then study the parameters to satisfy the requirement of the theory study and the practicality. In the before study, the experiential and semi-experiential relationship between spectrum parameters and wind parameters were obtained by site observation, numerical simulation, and so on. But these methods must depend on site date so closely that it can not be applied widely. In present paper, on the basis of the proposed spectrum with three parameters that obtained by Hou Yin-jun and Wen Sheng-chang, we established the controlling-model that depend on the dynamics formulas, and obtained the growth relationship between spectrum parameters (the spectrum variance , peak frequencymω0 , spectrum width B ) and wind parameters. Comparing the result in present paper with the before experiential relationship and check up it by using the site date, we can get the result as follow.From Fig.3, Fig9 and Fig10, it can be seen that the spectrum variances grow rapidly with the growth of the fetch at the beginning; going with the growth of the wind wave, the spectrum variances are growing more and more slowly; the spectrum variances stop growing when the wind wave grow sufficiently. It is consonant with objective laws of the development of the wind wave. Moreover, it can be proved that the results in this article are more accordant with the actual wave than before. So, we can say that, the new relationship between spectrum variances and fetch what is got in present paper by using dynamics theory are more reasonable than the foregoing result, and the new one can be applied extensively.The simplified relationship between wave steepnessδ, wave ageβand spectrum width B are obtained in this article. The simplified one describes the relationship of the three variances more directly, and can be use for derivation of theory more conveniently. Setting out from the physical essence, the new relationship between the spectrum variance m0 and the peak frequencyω0 what is controlled by the fetch is obtained. And the new relationship clarify that the foregoing results what are experiential are the special cases when the new result get the different numerical value. Therefore, it is reasonable that we believe that the m0 -ω0 relationship changes with the varying of dimensionless fetch. This is a sound improvement for traditional results.Furthermore, on the basis of the relationship between spectrum parameters and fetch, the relationship between the four kinds of wind wave spectra with three parameters and fetch are derived. On the basis, the developing model and rule of the wind wave spectra and the overshot can be described more clearly than before. It is proved that the model of wind wave spectra with three parameters is reasonable. At the mean time, it is also proved that the relationship between spectrum parameters and fetch is right.