本文應用質點影像測速 (Particle Image Velocimetry，PIV) 及氣泡影像測速(Bubble Image Velocimetry，BIV)，搭配數位影像處理技術 (Digital Image Processing，DIP) 等非侵入式量測技術，量測波浪通過複合式平台斜坡底床水位與流場變化情形，並藉由重複多次相同試驗運用整體平均法來分離碎波流場之平均與擾動速度。此外，由於碎波影像中的氣泡區域與非氣泡區域劃分不清，造成流場分析上的困難，故本文利用影像處理技術先行將影像中之氣泡與非氣泡區域界定之後才進行流場分析。本文也應用CCD (Charge Coupled Device) 攝影機以平視攝影方式拍攝一系列波浪試驗影像，並透過數位影像處理技術，自動偵測波浪連續水位變化資料。本文同時將所量測到之速度場進行平均速度、渦流、流線、紊流動能、水平及垂直紊流擾動量、紊流剪應力、紊流消散分佈等特性分析。
本文由實測數據分析波浪於複合式平台斜坡底床傳遞之流場時空變化。從量測結果顯示，波浪碎波後產生大量氣泡團，氣泡團剛形成時，其氣泡團內速度大部分以大於波速或是約等同於波速向前傳遞，最大速度可達1.26 ，而波浪水體內之速度分佈與淺水波理論大抵相符。氣泡團下緣靠近底床處因向離岸速度交會與分離形成速度緩速區。氣泡團內之紊流擾動強烈，其顯著的紊流動能、紊流剪應力效應皆發生於氣泡團前緣部分，並隨著波浪傳遞向離岸方向及底床擴散與衰減，而紊流消散分佈亦與紊流動能分佈趨勢一致，因此可得知由碎波所引發之氣泡團可能為近岸碎波帶能量消散的主要因素。

A laboratory measurement on the flow field, turbulence and wave energy of spilling breakers over a step-type profile is presented. Instantaneous velocity fields of propagating breaking waves on a step-type profile were measured using Particle Image Velocimeter (PIV) and Bubble Image Velocimeter (BIV). Variations of water surface elevation were observed by using Charge Coupled Device (CCD) cameras with horizontal posture. An automatic were detection technique was employed by digital image processing to save operational time. Evolution of the ensemble overage flows, vorticities, streamlines, turbulent kinetic energy, Reynold stresses and energy dissipations were obtained from analyzing the data.
The experimental results showed that the initial bubble velocity in the aerated region is faster than phase speed with a factor of 1.26. The velocity profiles are identical to the shallow water theory. It is found that a low flow velocity exists due to an opposite but equal onshore and offshore velocity. Significant turbulent kinetic energy and turbulent Reynolds stress are produced by breaking waves in the front of aerated region , then move offshore and decay. The calculated total energy dissipation rate was compared to that based on a bore approximation.

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