Underwater free-fall analysis of a solid cube for saturated sand settlement estimation
- Alternative Title
- 포화된 모래 침하 추정을 위한 정육면체의 수중 자유낙하 해석
- Abstract
- Free-fall installation is the oldest, simplest, and most popular manner to install an object from the high elevation to the lower elevation by using gravity acceleration. Utilizing gravity acceleration to serve human life is applied widely in many fields, for instance, the construction industry field, the military field, the outdoor entertainment activities, or especially the marine field, etc. Although the development of science and technology in recent decades, free-fall installation is still useful, especially in the marine field. For instance, the installation of an artificial reef by free-fall in Australia, Japan, Chinese, Korea, Vietnam, etc., or anchor installation when ships are mooring. That manner is always simple and economical but its accuracy and efficiency need to be examined when no study completely carries on that process from moving in the water to collide and embed in the seabed. For all that reason, this study proposed the method that can estimate that process by simulation and compare it to the experiment or mathematical theory. This study is divided into three steps to describe the process of free-fall installation on the seabed. In the first step, the drag coefficient of the solid cube is estimated in the air and water. A good agreement is obtained when comparing the simulation results with the previous experiment. In the second step, the process of the solid cube when moving in the water is calculated by theory and estimated by simulation. The velocity of simulation and theory result match not only in the shape of the trajectory but also its magnitude. Finally, the behavior of a solid sphere when embedding on the seabed is conducted by the simulation. The saturated sand is chosen to be seabed material to explore the settlement and the seabed stress after the collision. All simulation in this study is implemented by ANSYS software, for more details, the ANSYS CFX, the ANSYS Fluent, and the ANSYS AUTODYN are used in the first step, the second step, and the third step, respectively.
- Issued Date
- 2021
- Awarded Date
- 2021. 2
- Type
- Dissertation
- Publisher
- 부경대학교
- Affiliation
- Pukyong National University, Graduate School
- Department
- 대학원 해양공학과
- Advisor
- Won-Bae Na
- Table Of Contents
- CHAPTER 1 1
INTRODUCTION 1
1.Introduction 1
2.Purpose of the thesis 4
CHAPTER 2 5
DRAG COEFFICIENT OF A SOLID CUBE 5
1. Basic theories 5
1.1.The Navier-stokes equation 5
1.2.Turbulent flow 8
1.2.1.Classify the turbulent model 8
1.2.2.The linear eddy viscosity models 10
1.2.3.The non-linear eddy viscosity models 10
1.2.4.The Reynolds stress model (RSM) 11
1.3.Drag coefficient 12
2.Calculating the drag coefficient 13
2.1.Method and material 13
2.2.Boundary conditions 15
2.3.Mesh 16
2.4.Results 19
2.4.1.Drag coefficient in the air 19
2.4.2.Drag coefficient in the water 21
CHAPTER 3 23
UNDERWATER FREE FALL 23
1.Theory about underwater free-fall 23
1.1.Gravity force 23
1.2.Buoyancy force 23
1.3.Drag force 24
2.Calculating the movement of a solid cube in the water 25
3.Modeling the process of free fall in the water 28
3.1.Material and method 28
3.2.Boundary conditions 30
3.3.Mesh 35
4.Results 39
5.Comparison 44
5.1.Estimate the velocity from theory 44
5.2.Comparison of theory and simulation 45
CHAPTER 4 46
COLLISION OF THE SPHERE ON THE SEABED 46
1.Introduction 46
2.Simulation 47
2.1.Material 47
2.1.1.The Riedel-Hiermaier-Thoma concrete 47
2.1.2.CU-ARL sand model 53
2.2.Method 57
2.2.1.Lagrangian description 58
2.2.2.Simulation 60
2.3.Mesh 62
2.4.Boundary conditions 63
3.Results and discussion 68
3.1.Vertical velocity and settlement 68
3.2.The Von-mises stress of the seabed 72
CHAPTER 5 79
DISCUSSIONS AND CONCLUSIONS 79
ACKNOWLEDGMENT 84
REFERENCES 85
BIBLIOGRAPHY 88
THANKFULNESS 89
- Degree
- Master
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