Separation Of Incident Waves And Reflected Waves And Study Of Reflection Coefficients

This paper presents that the directional spectra and the reflection coefficients of the oblique and the multidirectional irregular waves on the co-exist wave field of incident wave and reflected wave have been studied. A modified two-points method is proposed that can be used to calculate the frequent spectrum and reflection coefficient of the oblique waves. For the multidirectional irregular waves, the directional spectra and reflection coefficients are obtained by the modified Bayesian directional method and the modified maximum likelihood method. A directional spectrum of the reflection coefficients is suggested and an empirical formula of the directional spectrum of the reflection coefficients for slope breakwaters are given by the model tests.In the analysis of the frequent spectrum and the reflection coefficients, based on Goda's two-points method which fit to the normal incident wave, a modified two-points method is derived that can be used to calculate the frequent spectrum and reflection coefficient of the oblique waves from which the frequent spectra of incident waves and reflected waves incoming in arbitrary angular, the bulk reflection coefficient and the frequent spectrum of reflection coefficient could be computed, also from which in theory the waves could be measured in two wave gauges which is disposed at any direction. The method has been used to separate the frequent spectra of incident waves and reflected waves of the composed wave that are simulated by a numerical method. The results shown that the frequent spectra of incident waves and reflected waves being computed are consistent with the target spectrum and the bulk reflection coefficient is too. The frequent spectrum of reflection coefficient is same as the input round the peak frequency. All above mean the MTPM is reliable.In the study of directional spectrum and reflection coefficient of multidirectional wave, firstly the wave elevation trains overlapped by the incident wave and the reflected wave of multidirectional wave are simulated in the method of a frequency corresponding to a direction. Then the composed wave trains are analyzed respectively by the MBDM and the MMLM. During the numerical study, the input factors include the various wave parameters, the different measuring wave system and the various reflect characteristic. The applying conditions of the MBDM and the MMLM for computing the directional spectrum and the reflection coefficient of multidirectional wave have been tested and the capabilities of the two methods are compared. The results show that of the resolution of the directional distribution is higher the MBDM than the MMLM and while of the resolution of the reflection coefficient higher the MMLM than the MBDM. The two methods are sensitive to the array disposal of wave gauges and the resolution power of the analyzing results by the polygon array is better, while the linear array worse. The wave gauge number of array and the distance between the array and the reflector can influence strongly the resolution power of the analyzing results. The spurious peak of the direction spectrum is not only relate to the interval distance between the gauge and the reflection line, but also relate to the chosen wave elements, the disposal of wave array, the main direction and the directional distribution of reflection coefficients. The results of the two methods for the single directional peak are better than the double directional peaks. The convergent speed of the MMLM is faster than the MBDM and also the stability of the MMLM is better than the MBDM. The resolution power of the MBDM is limited by its super parameters. After the systemic comparison of the two methods, the detail applicable conditions have been suggested.By the physical model tests and various methods, the frequent spectrum and the directional spectrum of incident waves and reflected waves of slope breakwater have been investigated systemically, and the bulk reflection coefficients, the directional spreading of reflection coefficients and the frequent...