本研究首先提出斜向波浪入射不透水底床的波揚與波降理論，用以瞭解波浪入射角度對波揚與波降所造成的影響，作為海岸工程應用之參考。理論分析得知，波揚與波降隨波浪入射角度的增加而減少。由試驗數據及現場實測資料的範圍顯示，本研究之波揚與波降理論，只適用於溢波與捲波的碎波型態。本研究並以水工模型試驗驗證波浪斜向入射時，碎波帶內波浪振幅與水深成線性關係的假設。再者，由理論分析結果發現，無因次波揚與碎波點波向角及海灘剖面形狀有關；且由於波揚的作用，導致灘線向陸地方向退縮，灘線移動的距離雖與剖面的形狀無關，但隨波浪入射角的增加而變小。
其次，本研究利用三個不等間距的測點所量測的波浪振幅，考慮波浪的線性淺化與折射效應，及地形造成的位相差，提出波浪斜向入射斜坡時的反射係數，及分離入射與反射波的方法，並探討模式的適用性及限制。經與前人數值模擬和試驗的結果相比較可知，本文的理論可推估不同地形變化的反射係數；並由水工模型試驗及數值計算結果，得知不同入射角度的波浪，入射斜坡上橢圓淺灘的反射係數分佈情況。本研究並對波高、水深及距離等量測上的誤差，進行敏感度分析，探討其對反射係數造成的影響。
本研究擴展Miles (1981) 之波浪通過擾變底床理論，推導斜向波浪通過不透水複合式系列潛堤的反射係數通式，對瞭解布拉格反射與共振現象，提出一個簡單又快速的方法。以兩群複合式矩形淺潛的反射係數通式，與水工模型試驗及數值計算所得結果比較後，顯示本研究的理論與試驗數據及數值計算結果均相當吻合。影響波浪通過複合式系列淺堤的反射係數的因素，包括波浪週波數、波浪入射角、淺堤堤寬、淺堤高度、淺堤總個數、淺堤間距，及群與群之間的間隔等；本研究針對這些影響因素加以分析探討，以瞭解其對布拉格共振效應的影響程度。

This study presents an analytical study for the wave setup and setdown, as induced by obliquely incident waves on an impermeable beach profile. The wave setup and setdown are found to decrease with the increasing wave obliquity. Notably, the inclusion of the wave obliquity in wave setup and setdown formulations offers a better physical suitability for engineering applications. The general solution effectively produces the limiting flow behavior with normal wave incidence, and the reduced results remained consistent with the available classical theories. Moreover, the results computed from the present theory are found to exhibit good agreement with the existing experimental data and field measurements. The present theory is primarily applicable to the spilling and plunging breakers across the surf zone, within which wave amplitude is assumed to be linearly related to the local water depth. Experiments were also conducted to verify the theoretical results, especially to confirm the validity of the assumption of linear dependence wave amplitude with the water depth in the case of obliquely incident waves. The theoretical formulation indicates that the dimensionless setup depends on wave angle at breaking and the shape of the beach profile; and it has a non-zero value at the original shoreline position, thus resulting in landwards advancement of the original shoreline.
A three-point method is also proposed for estimating wave reflection of an obliquely incident wave propagating over a sloping beach. The assumption of linear wave shoaling and refraction are applied to determine the changes in wave amplitude and phase shift due to variations in bathymetry. Wave reflection coefficient is estimated using the wave amplitudes measured at three fixed wave gauges with different distances from them. Based on the reflection coefficient and the measured amplitude, separation of incident and reflected waves is calculated. In addition, the applicability of the present theory is confirmed by comparing the results available from other theoretical and numerical models concerning the estimation of wave reflection. Within the framework of the present research, experiments were also conducted for the obliquely propagating wave over an elliptic shoal in a large wave basin, in order to investigate the effect of wave angle on the transmitted and reflected waves. The sensitivity of the present method with respect to the errors associated with the measurement of wave amplitudes, water depths and distance is also tested to provide a more accurate prediction of the reflection coefficient.
Miles’ (1981) theory for wave propagation on variable seabed is extended to derive a general expression suitable for describing the Bragg scattering effect and wave reflection coefficient of obliquely incident waves over composite artificial bars with different wave conditions and dispositions of bars. Experiments on Bragg reflections over doubly composite rectangular artificial bars were also performed in a wave flume to verify the validity of the present theory. It has been found that theoretical solutions remain in good agreement with the results obtained from numerical computations and the laboratory experiments. Despite the complex nature of such flows and the involvement of a number of variables in the mechanism of wave reflection (e.g. wave obliquity, shapes of bars, relative interval, relative spacing, relative bar heights, relative bar footprint and the number of bars), the present theory produced dependable results, which remained in good agreement with other theoretical results and experimental findings. Therefore, the present theory may serve as a valuable tool for estimating Bragg reflection coefficients and wave resonance for a number of engineering practices.

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