近岸區碎波帶為陸海環境交互重疊、相互影響之區域，因此該區域流場對於海岸結構物、懸浮物、漂砂與濃度擴散等均有密切關係。往昔許多學者針對不同碎波型態探討渦紊流的特性，並且提出渦流生成機制、碎波帶之流場可視化與紊流能量方程等重要結果，然而對於碎波帶完整之時空分佈則較少論述，故本文應用PIV量測技術探討溢波在1/20斜坡之碎波帶內部流場特性，並完整呈現碎波帶之流速與渦度時空分佈。
本研究係在成大水工試驗所斷面水槽進行。由於相機的拍攝解析度限制，因此共分成7個區域量測並應用空間組裝法(mosaic method)完整呈現整個碎波帶流場。量測範圍超過一個波長，從初始碎波至內碎波帶(inner surf zone)。碎波帶自由液面劇烈的變化，往往造成後續分析之困擾，因此本實驗利用影像處理法偵測自由液面之上下邊界，利用下邊界切割出感興趣之內部流場。平均速度則應用整體平均法分離，其穩定收斂次數為15次重複試驗，每試次的水位誤差均在0.3%內。

本論文完整呈現碎波帶流場結構的時空分佈。波峰速度在初始碎波時達到最大，其速度分佈與淺水波理論相符。波峰前緣與後端共生成兩個低速區，在波峰前緣為所謂的混攪區，而後端的低速區為前端的尾流與碎波過程中生成的延伸渦流所造成。在碎波過程中生成的渦流隨著波浪向岸傳遞同時向離岸方向延伸與拉長。

The hydrodynamics in surf zone has been an important subject for scientist and engineers due to its importance and complexity. The characteristics of vorticity and turbulence in surf zone were investigated by many researchers. Their researches demonstrate both qualitative and quantitative details in surf zone. However the temporal and spatial distributions of flow structures are not completely discussed. The objective of this paper is to investigate the internal flow structures of spilling breakers on 1/20 slope.

The experiments were conducted in a wave flume in Tainan Hydraulics Laboratory. Because the resolution of CCD camera is not high enough to capture the whole breaking process in one single frame, the whole measuring region is divided into 7 sub-areas by the mosaic method. The measured width of velocity distribution is over one wavelength from initiation of wave breaking to inner surf zone. The detections of water surface interface and entrained bubbles in images are the challenges in data analysis procedure. Therefore, an image process method is adopted to detect the edges of surface and obtain our interesting areas. The mean velocities are obtained by the ensemble average method with 15 repeats, the error of surface elevation is less than 0.3% in every test.

The temporal and spatial flow structures in the whole surf zone were completely presented in this thesis. The velocity of wave crest reaches maximum in the initial breaking region, and the distributions of velocities correspond with the shallow water theory. The head of lower speed region under the crest of bore is so called a mixing region. Behind it there still exists a decay of wake region due to the dissipation caused by the stretch of rotational structures generated from the head of the bore. The vorticties are generated in the breaking process, and they extend and elongate toward offshore as wave propagate onshore.

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