Based On Adaptive At Right Angles, Cutting And Mixing Grid Euler / Ns Equations Numerical Simulation

In modern aircraft design, there is an urgent requirement for accurate, efficient and easy-to-use numerical analysis tools. For this purpose, this thesis introduces recent progress in the generation and application of Cartesian grid with tree data structure and adaptive refinement. Coupled with hybrid grid techniques, Euler and Navier-Stokes equations are solved. Numerical simulation of the store separation and multi-element high-lift configuration are performed. The present work is focused on the following aspects:1. Based on tree data structure, the Cartesian grids about 2-D and 3-D configurations are generated using the surface-cutting procedure. In the course of grid generation, a two-step ray-casting algorithm to excluded cells inside the body and a cell-merging technique to avoid numerical instability are fully developed. After creating these surrounding grids, the cell-cutting algorithm is designed to perform geometry-based refinement of grids, and greatly improve the applicability and quality of grid generation.2. Using the tree data structure to manage the grids, the search and connectivity of data can be realized and quickened. The Omni-tree structure is developed, which supports anisotropic grid adaptations in any of the coordinate directions and allows high aspect ratio cells. Four separate data entities are defined, including nodes, lines, faces and cells, which is convenient to control information management in grids generation and flow calculation.3. A hybrid grid method is described which combines structured grids with unstructured triangular and Cartesian tree grids to provide great flexibility in discretizing a domain. According to this idea, computational grid of N-S equations solution is generated, which greatly extend the ability of the Cartesian grid.4. A 2-D and 3-D Euler equations and N-S equations are solved using the cell-centered finite volume method and four-step Runge-Kutta scheme on theCartesian grids with standard convergence acceleration techniques such as local time stepping, enthalpy and implicit residual smoothing. Solution-based grid adaptations are carried out, and efficiently capturing flow features.5. Coupled with the Cartesian grids, a store separation for wing/store configuration is studied. A computational method is developed with couples the governing equations of the unsteady flow field and the rigid-body dynamics in six degrees-o f- freedom.6. Facing the complex multi-element and high-lift configuration, a series of methods including multi-zone algorithm and face-to-face technique is developed to lower down the great difficulties of grid generation and finish flow calculation of high-lift system with the dual-time method.7. Many test cases are calculated to verify the above study. The cases are either real or standard testing models, including multi-element airfoil, wing-body configuration, cone/cylinder missile model and 3-D high-lift systems, etc. The results of present calculation are in good agreement with experiment data, and show flexibility and accuracy of the approaches.Base on the Cartesian grids, this thesis has targeted the development and integration of many algorithms and techniques such as adaptive refinement, Omni-tree data structure, hybrid grid method, etc. An analysis software and research methods are designed and developed for the steady-unsteady and viscous-inviscid flow complex systems and configuration.