Investigation of the Dynamic Characteristics of Shock Waves Propagating into Various Media

다국어 초록 (Multilingual Abstract)

This research delves into the intricate dynamics of shock waves propagating through multiphase environments, with a particular focus on their interaction with solid structures and downstream interfaces. Historically, the majority of studies examining fluid-structure interactions have concentrated on the upstream interface, overlooking the crucial role of downstream interfaces in determining overall energy partitioning and structural response. This thesis bridges this critical gap in understanding by comprehensively analyzing shock wave behavior across various configurations, including water-solid-air (WSA) and water-solid-water (WSW) systems.
The numerical framework employed in this research utilizes a coupled Eulerian-Lagrangian approach, enabling precise representation of both fluid and solid dynamics under high-intensity shock loading. This method ensures robust tracking of deformation evolution and energy distribution, providing essential data for predicting structural failure and optimizing designs in real-world scenarios.
Using advanced numerical simulations validated against analytical models, the study systematically investigates how shock waves traverse interfaces with differing acoustic impedances. The research reveals that the downstream interface plays an equally, if not more significant, role in shaping the wave dynamics compared to the upstream interface. This paradigm shift in understanding is pivotal for improving the design of structures exposed to high-energy transient events, such as underwater explosions or supersonic impacts.
This research explores the dynamics of wave bifurcation phenomena (longitudinal and transverse waves) in solids, which create distinctive strain concentration patterns at structural elements that exceed predictions from one-dimensional models by factors of 3 to 5. The longitudinal wave component dominates compressive deformation, while transverse waves induce shear deformation that spreads laterally through the material. At corner regions, the convergence of expansion waves from multiple directions amplifies strain concentrations, particularly in WSA configurations where reflected expansion waves interact with transverse components to create localized tensile stresses.
Key findings include the observation that WSA configurations produce extreme negative pressures, significantly increasing structural vulnerability compared to WSW systems. Additionally, the study establishes critical relationships between acoustic impedance mismatches, structural geometry, and energy dissipation mechanisms, offering valuable design principles for naval, aerospace, and defense applications. The thesis also highlights the importance of considering complete wave interference patterns across sequential interfaces to ensure accurate modeling of complex shock wave phenomena.
In summary, this work fundamentally reshapes the theoretical foundation of fluid-structure interaction by emphasizing the active participation of downstream interfaces in shock wave dynamics. By addressing these critical factors, the research offers engineers vital tools to enhance the resilience and efficiency of structures subjected to extreme loading conditions, paving the way for innovative solutions in marine, aerospace, and defense industries.

목차 (Table of Contents)

• Contents i
• List of Figures iv
• List of Tables vi
• Nomenclature vii
• Chapter 1 Introduction 10
• 1.1 Research background 10
• 1.2 Literature Review 11
• 1.3 Research Gap and Problem Statement 13
• 1.4 Research Objectives 15
• 1.5 Thesis Outline 17
• Chapter 2 Numerical Methodology 19
• 2.1 Governing Equation 19
• 2.2 Fluid Structure Interaction 21
• 2.3 Coupled Eulerian Lagrangian Solver 22
• 2.4 Energy Partitioning Analysis framework 24
• 2.4.1 Energy Components in the structure 24
• 2.4.2 Energy Partitioning Analysis of Fluid-Structure Interaction 26
• 2.5 Effective Strain Analysis in USI & DSI 27
• 2.6 Computational Domain 27
• 2.7 Grid Independence Study 29
• Chapter 3 Theoretical Framework 31
• 3.1 Conservation Laws in the Fluid 32
• 3.2 Continuity Conditions at the Upstream Interface 33
• 3.3 Solid Stress Propagation 34
• 3.4 Limitations of the Analytical Model 37
• Chapter 4 Shock Wave Propagation Dynamics 38
• 4.1 Propagation of Shock Wave across the Interface 38
• 4.2 WSW vs. WSA Comparison 43
• 4.3 Wave Bifurcation Phenomena 45
• 4.4 Longitudinal and Transverse shock wave propagation 48
• 4.5 Energy dissipation within a confined structure 50
• 4.6 Expansion Wave Dynamics 51
• 4.7 Corner Strain Concentration Mechanisms 53
• Chapter 5 Effects of Acoustic Impedance 57
• 5.1 Acoustic Impedance Effects in Fluid-Structure Interaction 57
• 5.2 Acoustic impedance impact on shock wave propagation 58
• 5.3 Energy dissipation Analysis in WSA & WSW configurations 60
• 5.4 Effective Strain Analysis in USI & DSI 62
• Chapter 6 Structural Response to Variable Thickness 66
• 6.1 Shock wave dynamics near interfaces of variable thickness 66
• 6.2 Wave Dynamics in Water-Solid-Air (WSA) Configurations 68
• 6.3 Wave Dynamics in Water-Solid-Water (WSW) Configurations 70
• 6.4 Energy Dissipation Analysis in WSA and WSW Configurations 72
• 6.5 Effective Strain Analysis at Fluid-Solid Interfaces 75
• Chapter 7 Conclusions and Future Work 79
• 7.1 Summary of Key Findings 79
• 7.2 Theoretical Contributions 80
• 7.3 Engineering Implications 81
• 7.4 Limitations of Current Approach 83
• 7.5 Specific Future Research Directions 85
• Bibliography 87
• Abstract 90
• Acknowledgments 92