高超声速近连续流的精细数值模拟与飞行器气动性能分析

Hypersonic near-continuum flows exhibit strong local rarefied effect and thermo-chemical nonequilibrium features. Accurate simulation of this type of flow has been the challenge of fluid mechanics, and is now required by the advanced design of hypersonic vehicles. This project aims to investigate the local rarefied gas effect and its impact on the aerodynamics of hypersonic vehicles flying in the near-continuum flow regime. Based on previous studies on several key problems of rarefied flow related to near space flight, it aims to develop further the proposed statistical particle simulation approach, and to improve greatly the numerical efficiency of the direct simulation Monte Carlo method, thus to perform dedicated simulation of the hypersonic near-continuum flow using large scale parallel computing. Along with simulations solving the Navier-Stokes equation, it will analyze the continuum breakdown criteria and local rarefied gas effect of hypersonic flow. By investigating the flows related to monatomic gas, diatomic gas with thermal nonequilibrium, gas mixture, and gas with thermal-chemical nonequilibrium in turn, this project should obtain aerodynamic data and help understand the behavior of local rarefied gas effect on investigated hypersonic vehicles.

高超声速近连续流具有强烈的局部稀薄气体效应和热化学非平衡特点，对此准确模拟一直是流体力学的难点和挑战，也是目前高超声速飞行器气动设计提出的更高要求。本项目针对具有尖前缘或复杂外形的飞行器在近连续流区的高超声速飞行，在过去对近空间稀薄气体流动的一些关键问题的研究基础上，尝试进一步发展高效的统计粒子模拟方法，从量级上提升直接模拟蒙特卡罗方法的计算效率，采用大规模并行计算对高超声速近连续流进行精细模拟；结合基于Navier-Stokes方程的数值模拟，分析连续性失效准则和流动的局部稀薄气体效应；分别通过对单原子气体、热非平衡的双原子气体、混合气体、以及考虑热化学非平衡气体流动的分阶段研究，获得飞行器的气动力和气动热数据，逐步摸清局部稀薄气体效应对高超声速飞行器气动性能的影响规律。

项目针对具有尖前缘或复杂外形飞行器在临近空间飞行的高超声速近连续流动的模拟和分析，从基于Navier-Stokes方程的连续流和基于Boltzmann方程的稀薄流两方面开展了近连续流的精细模拟研究。项目在大网格DSMC方法、DSMC方法的热化学模型、化学非平衡的微尺度机理、玻尔兹曼方程的BGK类模型及气体动理学格式的有效性、NS方程数值求解的网格依赖性、NS方程的降维模型、高超声速连续流动的驻点线热化学非平衡分析、激波管内的激波与边界层干扰、高超声速平板绕流问题的全流域分析、稀薄气体细长体/钝头体/模型飞行器三维流动分析、以及带电离反应的非平衡流动模拟等方面开展了具体研究。发展了内能交换的大网格DSMC方法、耦合SSA/Tao-leaping随机模拟方法、NS方程的驻点线降维模型，提出了广义BGK模型，修正了DSMC化学反应模型的能量配分方法，分析了化学非平衡的微尺度机理、气体动理学格式的有效范围、NS方程数值求解网格依赖性的数值根源，获得了稀薄气体效应对细长体/钝头体/模型飞行器三维流动的影响规律以及喷管内外带电离反应的非平衡流动图像，达到了预期目标。