臺灣博碩士論文加值系統

在潰壩實驗中，觀測自由水面下渠道幾何變化及流速是相當困難但有意義的，為了達成這個目標，本論文發展出一套方法應用在水工模型之潰壩實驗。
為了能觀察水面下的變化，實驗採用半渠道形狀，側邊為透明壓克力，再用雷射光照亮沿著潰壩渠道的三個斷面。這些斷面可以觀測潰壩過程中沖蝕的形狀演變。也可用來追蹤粒子在斷面彼此間的位置及量測流速。
同時，觀測形狀變化與流速的測量方法可運用在計算潰壩流量，並為此設計出兩種實驗模型，分別是固定壩與土砂壩，先用前者於穩定流的條件測試方法，後者期望能應用此方法來觀測潰壩渠道的變化。採用手動影像處理的方法，能成功測量形狀變化與流速，並估計出相對應的流量。在前者固定霸實驗中，計算出的流量結果與實驗室量測流量值達合理的吻合。實驗中也仍嘗試採用自動估算的方式，然而結果穩定性不足，仍有問題得克服，固最後未予以採用，仍以手動為主。

In dam breach experiments, it is often desirable but difficult to monitor the channel geometry and flow velocity below the water free surface. To achieve this goal, this thesis develops and tests a new approach applicable to laboratory experiments. To gain visual access, the experiments are conducted in a half-channel configuration, with a transparent sidewall taken as a symmetry plane. Next, laser light sheets are used to illuminate three transverse cross-sections along the breaching half-channel. These cross-sections make it possible to monitor the evolving shape of the erodible channel. They also allow the tracking of tracer particles from one cross-section to the next, hence measurements of flow velocity within the channel.
Together, the shape and velocity measurements can be used to estimate the water discharge through the breach. Two sets of experiments are conducted. Rigid dam experiments are first used to test the approach for steady flow conditions. Next, loose dam experiments are pursued to apply the approach to evolving breaching channels. Using manual image processing methods, it is found possible to measure both shape and velocity, and to estimate the corresponding discharge. For the steady rigid dam experiments, the resulting estimates are found to be in reasonable agreement with outflow measurements. Automated algorithms to capture and process particle tracks are also proposed, but problems remain to be solved before these algorithms can be used with confidence.

口試委員審定書 I
誌謝 II
摘要 IV
Abstract V
Outline VII
List of Figures X
Chapter 1. Introduction 1
1.1 Motivation 1
1.2 Past research on dam failure 5
1.3 Previous work on imaging methods 5
Chapter 2. Experimental Apparatus and Materials 7
2.1 Laboratory set-up 7
2.2 Rigid dam model 9
2.3 Loose dam model 11
2.4 Imaging set-up 14
2.4.1 Cameras and lasers 15
2.4.2 Calibration target 16
2.4.3 Pliolite tracer 17
2.5 Procedure 19
Chapter 3. Image processing methods 20
3.1 Camera calibration 20
3.1.1 3D calibration of high-speed oblique camera 21
3.1.2 2D calibration of sideview camera 23
3.2 Cross section measurements 24
3.3 Bed and water level measurements 28
3.3.1 Manual measurement using high speed camera 29
3.3.2 Manual measurement from sideview camera 30
3.4 Manual velocity tracking 32
3.5 Automated velocity tracking 33
3.5.1 Particle identification and tracking 34
3.5.2 Trajectory reconnection method 37
3.5.3 Laser crossing identification using brightness signal 42
3.5.4 Velocity estimation 48
Chapter 4. Results and comparison 49
4.1 Rigid dam results 49
4.2 Loose dam results 52
4.3 Comparison 61
Chapter 5. Conclusion and future work 64
References 66

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