Development and Evaluation of the Unstructured-Grid CFD

本研究旨在对非结构网格CFD(计算流体力学)进行提炼和检验，以便将其作为流体机械分析和设计的实用工程工具。在三年的研究中，取得了以下成果：(1)提出了一种在CAD-Defined模型上生成非结构曲面网格的新方法。该方法大大简化了非结构网格CFD的前处理过程。(2)提出了一种隐式时间积分和空间推进求解算法，减少了非结构网格上流动求解的计算时间。流动求解器的适用范围也扩展到燃烧和不可压缩流动。(3)提出了一种结合流动特征检测的解自适应精化方法。(4)提出了计算相对运动多体绕流的重叠非结构网格方法。(5)将非结构网格CFD应用于机翼、飞机、SCRAM喷气发动机、空腔和矩形管道流动等领域，对非结构网格CFD的精度和实用性进行了评估，结果超出了预期。研究过程中新提出的算法已经在国际学术会议上得到认可。在此研究过程中，非结构网格CFD的优化等几个新的方向也开始了。

The present study is to refine and examine the unstructured-grid CFD (computational fluid dynamics) so as to use it as a practical engineering tool for analysis and design of fluid machineries. In the three-year research, the following results were obtained.(1) A new method to generate unstructured surface grid on the CAD-define model was developed. With this method, the pre-processing procedure of the unstructured-grid CFD was significantly simplified(2) An implicit time integration and a space marching solution algorithms were developed to reduce the computational time of the flow solver on unstructured grids. The applicability of the flow solver was also extended to combustion and incompressible flows.(3) A solution-adaptive refinement method coupled with a flow-feature detection was proposed. This method was demonstrated of its effectiveness for the high-alpha delta wings.(4) An overset unstructured grid method was proposed to compute flow around multiple bodies with relative motions.(5) The accuracy and usefulness of the unstructured-grid CFD were evaluated by applying it to wings, airplanes, SCRAM jet engines, cavity and rectangular-duct flows, and so on.These results met more than our expectations. The newly proposed algorithms during the research have already been recognized in the international academic conferences. Several new directions of the unstructured-grid CFD, such as optimization, were also commenced during this research.