학위논문 (석사)-- 서울대학교 대학원 : 공과대학 기계항공공학부, 2018. 8. 김종암.The inside of the solid-propellant rocket motor has many difficulties for the numerical analysis because of the combustion of the propellant, the high temperature and high pressure flow and the structural deformation of the propellant. It involves complex physical phenomena which are influenced by each domain.
The analytical region of the solid-propellant rocket motor is divided into the fluid region, the structure region and the combustion region. The deformation occurs in each region over time. Therefore, it is necessary to generate a suitable grid for the analytical domain that deforms over time. In addition, it is necessary to generate suitable grids for the boundary layer for efficient and accurate viscous flow analysis.
When the grid deformation is periodical such as the aero-elastic analysis, the grid-moving method and the grid deformation method are used. On the other hand, because the solid-propellant rocket motor is a variation of the area due to the continuous combustion, unlike the above-mentioned problem, it is difficult to generate the grid by the two techniques. Therefore, it is necessary to regenerate the entire grid automatically during the analysis, which is called the grid regeneration technique. It is important that the grid regeneration technique usually has a stable and efficient grid generation process without user intervention.
In the case of internal flow geometries such as solid propulsion rocket engines, unlike ordinary external flow geometries, overlap between neighborhood grids occurs during the automatic grid generation process, and inevitably invalid grids can be generated.
In this study, it has purpose to develop an automatic grid regeneration program that automatically generates suitable grid for two-dimensional and three-dimensional solid-propellant rocket motors. To generate grids automatically, methods for automatically detecting poor grids and solving these problems without user intervention are needed. These methods are applied to the grid regeneration program. The several methods for improving the quality of the grid are introduced in this paper. In addition, the application of the developed grid regeneration program is conducted for several complex configurations and solid-propellant rocket motors. When the quality of the grid is checked in terms of skewness, better result can be obtained compared to the conventional methods. Since poor meshes are unexpectedly generated at the complex region, it can be applied to generate the grid of complex configurations.Chapter 1 Introduction 1
1.1 The phenomenon of Solid-propellant Rocket Motor (SRM) 1
1.2. Simulation on Solid-propellant Rocket Motors 3
Chapter 2 Numerical methods for grid generation 9
2.1. Delaunay triangulation [10,12] 9
2.2. Bowyer/Watson Algorithm 10
2.3. Quad-Tree data structure and Oc-tree data structure 12
2.4. Grid untangling method 14
2.5. Advancing-Layers Method (ALM) 15
2.5.1 Advancing-Layers Method for two-dimension 16
2.5.2. Advancing-Layers Method for three-dimension 20
Chapter 3 Grid generation methods for internal flows 26
3.1 Grid generation method for internal flow for two-dimension 26
3.2 Three dimensional grid generation methods for internal flows 34
Chapter 4 Grid generation program 41
4.1. Linking process with FSI solver 41
4.2. Overall procedure of grid regeneration module 42
Chapter 5 Aplications 47
5.1. Applications on complex geometries 47
5.2. Applications on solid-propellant rocket motors. 49
5.2.1 Two-dimensional Solid-propellant rocket motor 49
5.2.2 Three-dimensional Solid-propellant rocket motor 56
Chapter 6 Conclusion 59
Appendix A. Advancing-Layers Method by Pirzadeh [19,21] 61
Appendix B. Skewness and Area/Volume ratio [24] 63
References 64
국 문 초 록 67Maste
