Calculation Of Wave Height And Analysis Of Long Period Wave In Sheltered Water Area

Wave height distribution in harbors and its characteristics are concerned by oceanographers for a long time. The research of wave diffraction and long-period wave effects is meaningful in harbor planning and its construction. At present, calculation of wave diffraction is limited to characteristic waves method and no perfect mathematical model can effectively simulate irregular wave diffractions; meanwhile, the research of long-period wave is ignored in a long time in domestic academe.For the reasons above, two main sections are carried out in this paper.Firstly, a mathematical model for regular wave diffraction is introduced by applying the singularity distribution method solving Helmholtz type mild-slope equation, as the calculating module for regular wave diffraction, which can take the boundary reflection into account. By linear superimposing of constitutive regular wave diffraction on energy, as is recommended by the Code of Hydrology for Sea Harbor, a mathematical model based on the method of simulating irregular wave diffraction for irregular wave diffraction is established. Methods of frequency spectrum slicing and slicing numbers of frequency spectrum and directional spectrum are thoroughly analyzed and discussed. As a result, an effective spectrum slicing method and an optimal division number of frequency and direction are determined. On this basis, the influences of using different directional spectrums in the calculation modes are compared and calculated results of using various directional spectrums in diffraction calculation are compared in actual port. This provides a reliable reference for selecting frequency slicing method; number of segments of frequency and directional spectrum and the spectrum type. In comparison with survey data from physical model of actual topography, it is shown that the irregular diffraction model has a certain value of engineering application.Secondly, a numerical model for the separation between long period waves and short period waves was established on a FIR low pass digital filter which is based on window function. This mathematical model can separate long period wave from measured wave data. By doing this, the distribution of long-period wave can be obtained, thus it can provide references for berth design in harbors. And practical applications indicate that the numerical model has certain practical value in engineering.