Evolution of the Unstructured Mesh CFD for Multi-Disciplinary Problems

在非结构网格CFD的发展中，提出了几种提高曲面网格划分和混合网格划分能力和可靠性的算法。通过使用并行计算机，提高了流动求解器的计算效率。通过采用新的湍流模型，精度也得到了提高。非结构网格CFD程序对飞机、高尔夫球、昆虫等的绕流进行了数值模拟。为了对昆虫进行模拟，正在开发一种新的流动-结构耦合问题的程序，并将所开发的CFD程序应用于多段翼型进行验证。并将其推广到形状优化领域。在本研究中，发展了移动网格法来处理目标的形状变化。这种动态网格方法同样适用于具有可移动操纵面的飞机。在设计中，将逆方法与非结构网格CFD相结合。这对于设计具有自然层流机翼的超音速飞机是有效的，该飞机是由日本航空航天探索机构开发的。采用非结构网格CFD方法对一架近音速飞行的飞机进行了数值模拟。计算结果表明，近音速巡航存在一个最佳点。利用CFD对近声速飞机外形进行了优化设计，提高了升阻比；采用非结构网格CFD方法模拟了超音速冲压发动机内部的燃烧流动。这证明了本研究开发的非结构网格CFD程序的能力。本文还对微型燃气轮机内部的流动进行了研究。

In the developments of the unstructured-mesh CFD, several algorisms to improve the capability and the reliability of the surface meshing and the hybrid meshing were proposed. The flow solver was improved in its computational efficiency by utilizing the parallel computers. The accuracy was also improved by employing new turbulence models. The capability of the unstructured-mesh CFD code was demonstrated for flows around airplanes, golf balls, insects, and so on. For the simulation of insects, a new code for flow-structured coupling problems is under developing.The developed CFD code was applied to multi-element airfoils for the validation of the code. It was also extended to the shape optimizations. In this study, the moving mesh method man developed to treat the shape change of the target. This dynamic mesh method can treat the airplanes with movable control surfaces as well.For the design, the inverse method was coupled with the unstructured-mesh CFD. This was effective to design a supersonic airplane with natural laminar wings which had been developed under the Japan aerospace exploration agency. An airplane that flies at near-sonic velocity was investigated by using the unstructured-mesh CFD. The computed result showed that there was an optimum point to cruise at near-sonic velocity. Moreover, the CFD was utilized to optimize the shape of near-sonic airplane to improve the lift-to-drag ratio.The unstructured mesh CFD was applied to simulate the combusting flows inside a supersonic combustion ramjet engine. This demonstrated the capability of the unstructured mesh CFD code developed in the present study. Flow inside a micro-gas turbine was also investigated by the present code.