Strategy development for object-oriented multiblock grid generation and adaptation to complex geometries
The first part of the thesis deals with the strategy development for multiblock structured grid generation to complex geometries. Based on the grid generation practices over years, a set of grid construction rules is developed to provide the CFD engineer an object-oriented method for grid design. The essential core of the object-oriented method is to decompose a complex meshing task into a set of sub-tasks, which are treated individually at a lower level of both geometry and topology. The grid construction rules cover the questions of dealing with selection of meshing direction, generation of surface description and block topology building. To explain this grid design method, an example, dealing with a highly complex geometry, is demonstrated. The second part of the thesis deals with the strategy development for multiblock structured grid adaptation. Since a grid can be adapted with or without a flow solution, the terminologies passive and active grid adaptation are introduced to describe a solution-dependent or a solution-independent grid adaptation. Passive grid adaptation is performed by generating adequate block topologies, such that a local enrichment of grid points can be achieved. It consists of three concepts: one-dimensional clustering of grid lines, block encapsulation, and smart block. The method for solution-dependent grid adaptation is developed based on the idea of grid optimization. A grid is adapted by minimization of objective functions, in which relations among weight functions and grid line distribution are formulated. The measures for grid quality, such as smoothness, cell aspect ratio, and orthogonality, are formulated as control terms of the objective functions to improve grid quality. In addition, a concept of smart cell used for solution-dependent grid adaptation is proposed in this thesis.