新型结构/非结构耦合求解CFD软件研究与开发

Computational fluid dynamics (CFD) has been playing more and more important role in aerospace vehicle design and study of flow mechanism. So many CFD codes, as well as some commercial CFD software, have been developped during the last two decades. Generally, these flow solvers can be classified into two types: structured solvers and unstructured solvers. The structured solvers, which adopt the finite difference methods or the finite volume methods, can only run on structured grids, including the multi-block patched grids and the overlapping or Chimera grids. The unstructured solvers (based on the finite volume methods or the finite element methods) usually run on unstructured grids. For complex configurations, the structured/unstructured hybrid grid techniques represent the trend of grid generation method. However, allmost all of the flow solvers for hybrid grids should transfer the data structure of the strucutred grids into that of the unstructured grid. Therefore, the properties of high-efficiency and high-accuracy of structured solvers are not inheritted in these cases. .In this project, we will develop a hybrid flow solver, in which the strutured solver runs on the structured grids, while the unstructured solver runs on the unstructured meshes. Two sub-solvers are integrated into a flow solver, and runs synchronously to reach a balance between efficiency, accuracy and flexibility for complex geometries. To develop this new-generation flow solver, the frame structure and the data structure are the main issues in this project. In order to enhance the universality and expansibility of the solver, the Object-Oriented technique and C++ langurage will be adopted for code programming. Some basic Classes will be extracted and defined to satisfy the requirement of large-scale parallel CFD simulation and other purpose. The structured solver and the unstructured solver, as well as other special solvers (such as solvers for turbulence models, MHD eqautions, high-order numerical schemes), will exist in the code as a sub-class or a derivative class. In order to store and manage all kinds of data during simulations, a concept of 'Running Data-Base' will be introduced.

针对未来多学科耦合计算的需要，本课题拟开发针对结构网格和非结构网格耦合计算的大规模并行CFD计算软件。着重研究大型通用CFD软件的体系结构、数据结构和混合求解算法。通过设计合理的体系结构，提高软件的扩展性，利于未来多学科耦合计算问题中，集成不同模型的解算器；设计灵活的数据结构，提出"运行数据库"的概念，提高CFD计算过程中各种数据存储的规范性；针对结构网格和非结构网格的特点，结合二者优势，开发一种结构/非结构解算器的混合求解算法，在结构网格上采用结构算法，而同时在非结构网格上采用非结构算法。

针对未来多学科耦合计算的需要，本课题开发针对结构网格和非结构网格耦合计算的大规模并行CFD软件。针对结构网格和非结构网格的特点，结合二者优势，研究一种结构/非结构解算器的混合求解算法，在结构网格上采用结构算法，而同时在非结构网格上采用非结构算法。课题主要完成了以下几方面的工作：（1）调研国内外CFD软件，设计了软件总体运行方案，设计了满足结构/非结构耦合计算以及多学科耦合计算需求的体系结构及数据结构，撰写了软件概要设计报告、详细设计报告；（2）编写代码，完成了软件原型系统，进行了初步的算例验证工作；（3）实现了NS方程的结构/非结构耦合求解功能，进行了混合解算器计算效率研究，加载了湍流模型方程、化学反应方程解算器等；（4）撰写软件理论手册、设计手册，开展软件的测试工作，撰写软件测试报告。通过以上工作，开发出了新型结构/非结构耦合求解CFD软件的1.0版本，该软件初步具备多学科耦合计算能力，能自由加载不同的解算器，并行计算效率高，1024 个分区的计算效率达到 50%以上。课题研究成果提升了自主研制CFD软件的能力，逐步推出了具有自主知识产权的软件产品和品牌，推动国内CFD软件的发展。