臺灣博碩士論文加值系統

氣墊船 (Hovercraft) 又可稱為全墊式氣墊船(Air-cushion vehicle)，為同時具有越過陸地、水面、泥濘地或其他性質表面越野能力之水面載具。對於軍用氣墊船進行存活性設計時，其必須具備承受極端負荷狀況如水下爆震 (Underwater explosion, UNDEX) 之能力。本論文利用類水牛級 (Zubr-class like) 氣墊登陸艇 (Air–cushioned landing craft, LCAC) 為對象，建構耦合水域場及結構體之有限單元數學模型，以音響-結構耦合分析法(Acoustic-structure coupling method) 及耦合尤拉-拉格朗日分析法(Coupling Eulerian Lagrangian method)，探討於爆震負荷下之結構動態反應。
首先利用Kwon, Ramajeyathilagam及 Klaseboer等人實驗資料，針對圓筒殼及矩形平板於水下爆炸產生之主震波負荷及氣泡脈衝負荷狀況下之結構反應，驗證本論文建構分析程序及方法，證明其可靠性；進行氣墊船之抗水下爆震分析時，係以9kg TNT炸藥為震源，得到系列加速度、速度、結構變形及水域場爆壓等動態歷程分析成果，並探討氣墊船船體主結構 (Body structure) 及襯 裙 (Skirt) 之動態反應，本論文研究成果並可觀測氣墊船承受爆震時之流場噴流效應 (water-jet effect) 及不同區域位置之結構反應，研究成果可供氣墊船或船舶結構設計者進行水下爆震設計時參考使用。

A hovercraft, also known as an air-cushion vehicle or ACV, is a craft capable of traveling overland, water, mud or ice and other surfaces. Hovercraft must be designed to survive in the extreme loading conditions, such as an underwater explosion (UNDEX). However, for the previous study, the UNDEX response was primarily studied focus on ships, submarines and the other submerged structures. For this reason, this study selected a finite element model based Zubr-class like LCAC (Air-cushioned landing craft) subjected to UNDEX, dynamic responses of structure analysis were conducted. This study develops a procedure which links together the finite element method (FEM), Acoustic-Structure Coupling (ASC) method and Coupled Eulerian-Lagrangian (CEL) method to simulate an UNDEX and investigated the survival capability of a damaged craft. First, finite element model tests are conducted to verify and validate the propagation of shock response and bubble damage generated by an underwater explosive experiment of Kwon, Ramajeyathilagam and Klaseboer, which process the precision of the calculation model and method. The numerical model and method can be applied in practice. Second, finite element simulations of the hovercraft model subjected to UNDEX simulation that detonates of 9kg of TNT were presented using the same method. The characteristic of body structure and skirt responses of the hovercraft model are discussed. The numerical results show that besides global response, the body structure of hovercraft sustains severe local response especially is the main deck and skirt. In the case of UNDEX bubble simulation in free field. It is found through the calculation that the oscillation of bubble under the effect of gravity, water jet formation, and pressure pulse in the bubble collapse. It has been found that the appear the high-speed flow region in the middle of the bubble develops to form the water jet reaching approximately at 6.4 m/s in an upward direction when the bubble becomes doubly connected at 0.6s. After that, the velocity of the water jet decreases rapidly.

TABLE OF CONTENTS
Inside Front Cover
Signature Page
中文摘要 ..........iii
ABSTRACT..........iv
ACKNOWLEDGEMENTS..........vi
TABLE OF CONTENTS..........vii
LIST OF FIGURES ..........x
LIST OF TABLES ..........xiii
NOMENCLATURE ..........xiv
ABBREVIATION ..........xvii
Chapter I. INTRODUCTION ..........1
1.1 Background and Purpose.......... 1
1.2 Thesis Overview..........4
Chapter II. THEORETICAL BACKGROUND..........6
2.1 Air Cushion Vehicle: The Special Feature of Hovercraft..........6
2.2 Underwater Explosion (UNDEX) Phenomena..........8
2.2.1 Underwater explosion shockwave phenomenon..........10
2.2.2 Underwater explosion bubble phenomenon..........12
2.3 Acoustic-Structure Coupling Method (ASC)..........15
2.4 Coupled Eulerian-Lagrangian (CEL)..........19
2.5 Equation of State..........24
2.5.1 Us-Up EOS..........24
2.5.2 Ideal gas EOS..........25
2.6 Fracture Theory..........27
2.6.1 Introduction..........27
2.6.2 Damage initiation and evolution for ductile metals..........30
Chapter III. VALIDATION OF THE NUMERICAL METHOD..........33
3.1 ASC Method Validation..........33
3.1.1 Simulation and Damage of A Cylinder Subjected to UNDEX..........33
3.1.2 Rectangular Plate Subjected to Underwater Shock used ASC Method..........41
3.2 CEL Method Validation..........48
3.2.1 Simulation of Bubble and Free Dynamics in UNDEX..........48
3.2.2 Rectangular Plate Subjected to Underwater Shock Used CEL Method..........56
Chapter IV. MODELING AND SIMULATION..........60
4.1 Zubr-Class Modeling..........60
4.2 Underwater Explosion Simulation: Structural Response..........64
4.2.1 Dynamic Response of Air Cushion Vehicle with Shock-wave..........65
4.2.2 Dynamic Response of Air Cushion Vehicle with Bubble..........67
4.3 Underwater Explosion (UNDEX) Bubble Simulation..........68
Chapter V. SIMULATION RESULTS AND DISCUSSION..........70
5.1 Underwater Explosion Simulation: Structural Response..........70
5.1.1 Dynamic Response of Air Cushion Vehicle with Shock-wave..........70
5.1.2 Dynamic Response of Air Cushion Vehicle with Bubble-pulse..........81
5.2 Underwater Explosion (UNDEX) Bubble Simulation..........92
Chapter VI. CONCLUSIONS..........96
6.1 Conclusions..........96
6.2 Future Work..........98
APPENDIX..........99
A.1 UNDEX simulation of air cushion vehicle with shock wave..........99
A.2 UNDEX simulation of air cushion vehicle with bubble pulse..........116
REFERENCES..........123
CURRICULUM VITAE..........126

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