臺灣博碩士論文加值系統

本論文以探討潰壩發生時水面流及底床載在壩體下游處的交互作用關係為主題，並利用小尺度的實驗來進行模擬。潰壩主要是由水的流動及底床載的運移而產生，因此選用兩種不同大小及材質的顆粒分別作為水表面及底床載的軌跡追蹤，藉由此方案可以使兩種觀測結果同步，降低對於實驗重複性的需求。在過去的經驗中，粒子速度測量追蹤技術常用於側面的實驗觀測與分析，本研究採用俯視觀測來進行分析，其因為俯視可以直接觀察地形的變化並且不影響分析流場之技術。在地形測量方面，採用由Agisoft軟體公司所提供的軟體Photoscan。 此軟體可以利用照片來還原地形，並輸出成數值地型模型。利用投影的方法將速度場資料與地形資料結合，可以得到三維的速度場。除此之外，利用質量守恆方程式推算地形變化率，並與數值地形模型結果比較。最後由實驗結果發現與真實事件的地形相似，以及水與底床載之速度為正相關。本研究在於潰壩的模擬上有不錯表現，在於追蹤速度的技術上可以達到同時分析兩種不同類型之顆粒。

Dam breaching consists of water flow and sediment transport. The connections between water and bed-load velocity and dam breach topography changes in downstream are the purpose in this study. Previous researches are devoted to observe dam breach phenomenon from side view. From top view, the flow field changed by terrain and the surface flow can be observed. A simplified laboratory experiment is conducted to obtain horizontal two dimensional velocity fields. In order to compare water surface and bed-load velocity, we use two different color and density particles to record water and bed-load motion synchronized. The particle tracking velocimetry (PTV) method is used to analyze velocity fields. The topography is acquired as Digital Elevation Model (DEM) using the software Photoscan, Agisoft. According to the DEM, the changing of topography can be discussed. The flow field can be projected to topography as 3 dimensional flow field. Using this approach, we successfully obtain both water surface velocities and bed-load velocities. We found that water surface velocity will affect the bed-load velocity. Besides, the topography have similar pattern to real dam breach events. Finally, the mass conservation can be used to estimate topography changing rate of bed-load if particles velocities are given.

CONTENTS

口試委員會審定書 #
誌謝 i
中文摘要 iii
ABSTRACT iv
CONTENTS v
LIST OF FIGURES vii
LIST OF TABLES xvi
Chapter 1 Introduction 1
Chapter 2 Experimental Set-up and Procedure 4
2.1 Experiment set-up 5
2.1.1 Experiment channel system 5
2.1.2 Image measurement facilities 7
2.2 Particle material 8
2.3 Experiment procedure 10
2.3.1 Experiment arrangement 11
2.3.2 Calibration 14
Chapter 3 Image Method 18
3.1 Pre-processing and particle tracking velocimetry 18
3.1.1 White particle filter 18
3.1.2 Black particle capture 20
3.1.3 Particle tracking velocimetry 22
3.2 Agisoft photoscan application on recording topography 23
3.3 2D flow velocity project on 3D topography 26
Chapter 4 Result and Analysis 27
4.1 Repeatability performance 27
4.2 Topography processes 33
4.3 Particle tracking velocimetry 45
4.4 Bed-load transport verification 58
4.5 2D flow field project on topography. 63
Chapter 5 Conclusion 74
REFERENCES 76

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