本研究利用高取樣頻率的三軸聲波式單點流速儀ADV，觀測底床剪應力與擾動特性在波流交互作用下之變化。研究地點包含實驗水槽、愛河以及屏東後灣外海，剪應力估算方法是以慣性消散法與擾流動能法為主，並輔以渦流相關法。首先由實驗水槽的量測結果顯示，底床剪應力會隨著流速和波高的增加而變大，其中又以流速的影響最為重要，流速和剪應力兩者間有著正向的關係。
現場實驗的結果可以分成幾種類型來討論，第一種為流速小且波浪小的情況，愛河下游是典型的平均流速小但水質混濁的區域，觀測期間ADV的Correlation皆有達到90％以上，但因為流速太小所以並沒有產生明顯剪應力，u*全都低於1 cm/s，使得此區域的堆積效應遠大於侵蝕作用，河床底部有著很厚的淤泥；2011年4月的後灣實驗期間流速和波高均很小，且Correlation和u*也不高，因為在開放的河口環境下水質很清澈，若無底床擾流的產生使水體變濁，訊號品質就會很低。第二種為流速大且波浪小的情況，例如2011年4月的後灣實驗，最大流速達25 cm/s，產生的剪應力大且訊號品質優良，曳力係數Cd為0.0021，能譜圖中的sub-range比較寬，u*皆符合使用慣性消散法的條件，第三種為流速小但波浪大的情況，發生於2011年7月的後灣實驗，最大波高約為90 cm，u*集中在1 cm/s上下，回聲強度和濁度、波高有正向關係，波浪軌道速度會造成顯著的底床剪應力。

A 3-axis acoustic Doppler Velocimeter (ADV) with high sampling rate was used to measure the bed shear stress and turbulence under wave-current interaction conditions in this study. Experimental sites include laboratory tank, Love River in Kaohsiung and Howan coastal waters in Pingtung. Bed shear stress is estimated primarily by the inertial dissipation method, also by the turbulent kinetic energy method and eddy correlation method. Results of the laboratory experiments indicate that the bed shear stress increases as both the flow speed and wave height increase, and the flow speed is a more important factor.
Field experiments can be divided into several types. The first type is under slow flows and calm waves. Love River is a typical condition of this type with turbid waters and a low flow speed. During the experimental period the ADV correlations reach 90% or more. Because the river flow is quite small, no significant bed shear stress is produced and u* is mostly less than 1 cm/s. As a result the deposition effect is much larger than erosion, thus a very thick layer of mud is formed on the riverbed. The observations in Howan in April 2010 also reveal the condition of slow flows and small waves, and the bed shear stress is also quite small. Due to the factors of clean coastal waters and weak turbulence in this season, the quality of ADV signals is poor. The second type is under large flows and small waves, as shown from the observations of Howan in April 2011, during which the maximum speed reached 25 cm/s and wave heights less than 20 cm. In this experiment the shear stress is large, the u* are mostly greater than 0.8 cm/s and the value of the drag coefficient is 0.0021; the ADV signals have good quality and the inertial sub-range is well defined. The third type is under weak flows and large waves. The observations of Howan in July 2011 show significant rainfall and maximum wave heights of 90 cm. In this case the u* are mostly centered around 1 cm/s. The acoustic backscatter intensity is positively correlated with the turbidity and wave height. Sizable bed shear stress induced by the orbital velocity of waves contributes a significant part to the total bed shear stress.

謝誌…………………………………………………………………………………I
中文摘要……………………………………………………………………………II
英文摘要……………………………………………………………………………III
目錄…………………………………………………………………………………V
圖目錄………………………………………………………………………………VII
表目錄……………………………………………………………………………VIII
第一章、 前言……………………………………………………………………1
1.1 底床邊界層結構…………………………………………………………1
1.2 前人研究…………………………………………………………………2
1.3 研究動機和目的…………………………………………………………4
第二章、實驗設計…………………………………………………………………6
2.1 儀器介紹…………………………………………………………………6
2.2 實驗配置…………………………………………………………………7
2.2.1 造波水槽………………………………………………………………7
2.2.2 愛河下游河道…………………………………………………………7
2.2.3 後灣海域………………………………………………………………8
第三章、資料分析…………………………………………………………………15
3.1 資料來源…………………………………………………………………15
3.2 ADV資料品管……………………………………………………………15
3.3 分析方法…………………………………………………………………17
3.3.1 剪應力………………………………………………………………17
3.3.1.1 渦流相關法………………………………………………………17
3.3.1.2 TKE法……………………………………………………………17
3.3.1.3 慣性消散法………………………………………………………19
3.3.2 回聲強度BSI…………………………………………………………20
3.3.3波浪水粒子軌道速度和產生底床剪應力……………………………21
第四章、實驗結果與討論…………………………………………………………25
4.1 水槽實驗…………………………………………………………………25
4.2 流速小且波浪小的情況……………………………………………………32
4.2.1 愛河觀測………………………………………………………………32
4.2.2 後灣2010年4月觀測………………………………………………37
4.3 流速大但波浪小的情況……………………………………………………41
4.4 流速小但波浪大的情況……………………………………………………47
第五章、結論……………………………………………………………………55
參考文獻……………………………………………………………………………58

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