Incipient Motion Criteria of Uniform Gravel Bed under Falling Spheres and Natural Stones impact in Open Channel Flow
개수로 흐름에서 침강하는 돌이 있을 때 균일자갈 하상의 초기운동 조건
- 주제(키워드) 도움말 Incipient motion , Sediment transport , Critical shear stress , Drag force , Saltation.
- 발행기관 강릉원주대학교 일반대학원
- 지도교수 도움말 박상덕
- 심사위원 백중철, 윤찬영
- 사용가능일 20190201
- 발행년도 2018
- 학위수여년월 2019. 2
- 학위명 석사
- 학과 및 전공 도움말 일반대학원 토목공학과
- 실제URI http://www.dcollection.net/handler/kangnung/000000010327
- UCI I804:42001-000000010327
- 본문언어 영어
초록/요약 도움말
The investigation of the incipient motion of the sediment transport is crucial to control the stability of the bed and banks of a natural alluvial channel in response to the prevention of the hazards and infrastructure worldwide. Previous studies on the criteria of the incipient motion and its influencing factors have been well documented. However, those researches have tended to focus only on the incipient motion criteria under uniform flow condition, grain properties, channel slope, and relative depth. Less attention has been paid to the sediment transport induced by the inflowing from debris flow that frequently occurs in mountain river due to a heavy rainfall. This phenomenon could not only add additional forces to the sediment transport in the bed of the river, but also affect and change the direction and the magnitude of the sediment motion. In this study, evaluations on incipient motion of uniform gravel under falling spheres and natural stones impact using the flume channel with 9 m long, 0.6 m wide and 0.6 m deep. The slope of the channel was set from 0.8 % to 2.3 % with 0.031 m3/s to 0.137 m3/s water discharge. The sorted median grain size d50 (2.32 mm, 6.50 mm, and 13.05 mm) was used. The sphere diameters were chosen to be 4 cm, 6 cm, 8 cm, and 10 cm, whereas the nominal diameter of natural stones were 7.23 cm, 8.31 cm, and 9.31 cm. The effects of the falling spheres and natural stones were investigated for the condition where gravel bed nearly close to the critical incipient motion condition. Based on the results obtained, the motion of gravel bed under the impact of the falling spheres and natural stones were interpreted using the threshold curve. The size, weight and shape of the falling spheres and the natural stones have significant effects on the movement condition of the gravel bed. In addition, the relationship between drag force and the horizontal movement length of the spheres and natural stones were plotted. The saltation trajectories, the frequency of the rolling length, saltation length, and saltation height of the gravel bed were also investigated.
more목차 도움말
TABLE OF CONTENS
Abstract iv
TABLE OF CONTENS vi
LIST OF FIGURES ix
LIST OF TABLES xi
ACKNOWLEDGEMENT xii
CHAPTER 1 INTRODUCTION 1
1.1 Research background 1
1.2 Problem statement 2
1.3 Objectives of this study 2
1.4 Dissertation outline 3
CHAPTER 2 LITERATURE REVIEW 4
2.1 Incipient motion 4
2.1.1 Overview of incipient motion 4
2.1.2 Analysis of threshold diagram 5
2.2 Velocity distribution in turbulent flow 7
CHAPTER 3 EXPERIMENTAL STUDY 10
3.1 Laboratory facilities 10
3.1.1 Flume channel10
3.1.2 Acrylic glass sill14
3.1.3 Gravel bed.15
3.1.4 Spheres and natural stones17
3.1.5 The digital camera19
3.2 Experimental design 20
3.2.1 Threshold curve20
3.2.2 Characteristics of falling spheres and natural stones.21
3.2.3 Criteria of the gravel bed under falling spheres and natural stones impacts23
3.3 Experimental Setup and Procedure 25
CHAPTER 4 RESULTS AND DISCUSION 28
4.1 Threshold diagram 28
4.2 Characteristics of falling spheres and natural stones 31
4.3 Criteria of gravel bed under impacts of the falling spheres and natural stones 36
4.3.1 Trajectories of saltation38
4.3.2 Frequency of the grain motion41
CHAPTER 5 CONCLUSIONS 44
5.1 Summary and conclusions 44
5.2 Recommendations for future Research 45
REFERENCES 47
NOTATION 51
Appendix A. Summary of experimental data 53
Appendix B. The threshold diagrams 56
Appendix C. The velocity profiles 62
