The present work computationally investigated the combined effects of thermal non-equilibrium and chemical reactions on hypersonic air flows around an orbital reentry vehicle during its reentry. The chemically reacting gas flow around the orbital vehicle was simulated for actual reentry trajectories, with a computational solver based on the Navier–Stokes–Fourier equations. Hypersonic flows for a wide range of flying altitudes from 40 to 80 km were examined. We first analyzed important properties such as Mach number, trans-rotational temperature, vibrational temperature, chemical species composition, and surface properties such as the maximum heat flux for various altitudes. We then investigated the distribution of heat flux on the surface of the orbital reentry vehicle and the coupled effects of thermal non-equilibrium and chemical reactions on the hypersonic air flows. The computed heat flux results were compared with actual flight test data obtained during reentry of the orbital vehicle. The computed results were found to be in excellent agreement with the flight test data until an altitude of 60 km. Finally, we propose an explanation why heat flux was over-predicted around 70 km altitude but returned to better agreement at the higher altitude of 80 km. The phenomenon is based on two competing effects: the shortcoming of the first-order law of heat flux in the NSF equations and the inaccurate description of the effects of thermal non-equilibrium on chemical reactions in Park’s two temperature model.

中文翻译：

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非平衡热和化学反应对轨道再入飞行器周围高超声速气流的综合影响

目前的工作通过计算研究了热非平衡和化学反应对再入轨道再入飞行器周围高超音速气流的综合影响。使用基于 Navier-Stokes-Fourier 方程的计算求解器模拟了轨道飞行器周围的化学反应气体流，用于实际再入轨迹。检查了从 40 到 80 公里的各种飞行高度的高超音速流动。我们首先分析了重要的特性，如马赫数、反旋转温度、振动温度、化学物质组成和表面特性，如不同高度的最大热通量。然后，我们研究了轨道再入飞行器表面的热通量分布以及热非平衡和化学反应对高超声速气流的耦合影响。计算出的热通量结果与轨道飞行器再入期间获得的实际飞行测试数据进行了比较。计算结果与飞行测试数据非常吻合，直到 60 公里的高度。最后，我们提出了一个解释，为什么在 70 公里高度附近高估了热通量，但在 80 公里的更高高度恢复了更好的一致性。这种现象基于两个相互竞争的影响：NSF 方程中热通量一阶定律的缺陷和 Park 的两个温度模型中对热非平衡对化学反应的影响的不准确描述。