稀薄流区高超声速飞行器表面缝隙流动结构及气动热环境的分子模拟

针对高空稀薄流区的高超声速飞行器表面缝隙或缺陷结构导致的局部气动加热问题,采用直接模拟Monte Carlo(DSMC) 方法研究了70、75、80km和90km等4个飞行高度下稀薄流区高超声速缝隙流动问题,考虑稀薄气体效应和三维效应对缝隙内部流场结构和热流的影响。结果表明:上述飞行高度下,外部流动的分离和再附在缝隙内部形成一个充满腔体的单涡结构；稀薄气体效应对缝隙内部流动结构和壁面热流影响明显,随着高度的增加,主涡涡心上移,其形状逐渐变得“扁长”,右上角逐渐变尖,热流越来越集中分布于缝隙下游侧面的顶部区域；三维缝隙效应阻碍来流气体分子进入缝隙,导致主涡涡心上移,二维缝隙假设会高估缝隙表面的热流。 

Monte Carlo simulation for the flow-field structure and aerodynamic heating due to cavities on hypersonic vehicle surfaces in the rarefied flow regime

In order to solve the problem of local aerodynamic heating due to cavities or imperfections on the hypersonic vehicle surfaces, the direct simulation Monte Carlo (DSMC) was employed to investigate a rarefied and hypersonic flow over cavities at the altitudes of 70, 75, 80km and 90km, while considering the effects of rarefied gas and three-dimensional property on flow-field structure inside the cavity and heat flux over the cavity surfaces. It showed that one primary recirculation region was formed as a result of flow separation and reattachment at aforementioned altitudes. In addition, rarefied gas effect played an important role in flow-field structure and heat flux; as the flight altitude increased, the primary vortex became slender, with its core moving up and top-right-corner part sharpening; and the heat flux consequently concentrated to the top region of the downstream surface of the cavity. Moreover, the inclusion of the third-dimension would preclude main-stream gas molecules from penetrating into the cavity, causing the rise of the core of the primary vortex, and an assumption of two dimensionalities resulted in an overprediction of heat transfer to the cavity surfaces.