热化学非平衡来流条件下热化学模型影响研究

Effects of Thermochemical Models in Case of Thermochemical Nonequilibrium Inflow

关键词:  热化学非平衡  双温度模型  斜激波  前缘钝化  高焓激波风洞实验  数值模拟

Key words:  Thermochemical nonequilibrium  Two-temperature model  Oblique shock wave  Leading edge bluntness  High enthalpy shock tunnel experiment  Numerical simulation

摘要:

为研究热化学非平衡来流条件下热化学模型等计算设定对斜激波压缩流动计算结果的影响，针对尖劈构型和相应的前缘钝化构型的高焓激波风洞实验，采用多种计算设定开展详细的数值模拟研究。计算结果表明，计算采用不同热化学模型，以及来流设定为振动冻结/平衡/非平衡状态，会导致斜激波激波角等参数存在一定差别，其中激波角差别可达约2%。当来流速度一定时，过斜激波后分子内能增量在平动转动能和振动能上的分配方式的差别决定了激波角的差别。前缘钝化情形下，采用不同计算设定所得激波角之间的关系和尖前缘构型的规律一致；但是，采用不同计算设定所得斜激波到壁面距离之间的关系和尖前缘构型的规律有差别，这源于钝化前缘的激波脱体距离的影响。对于自由来流下的斜激波压缩流动问题，若考虑了分子振动能激发但未考虑热力学非平衡（例如热完全气体模型、考虑空气反应的单温度模型等），就斜激波激波角等参数而言，计算误差比量热完全气体模型计算误差更大。

Abstract:

This paper aims at studying the effects of computational settings， especially the thermochemical model， on the simulation of oblique shock compression flow whose inflow is in thermochemical nonequilibrium. Detailed numerical simulation using various computational settings is conducted regarding the high enthalpy shock tunnel experiments of a wedge model and the corresponding blunt leading edge model. When different thermochemical model is used， and when the inflow is in vibrational frozen/ equilibrium/ nonequilibrium， the resultant parameters of the oblique shock are different， in which the difference in shock angle can reach 2%. If the inflow velocity is fixed， the difference in shock angle is decided by how the increase in molecular internal energy across the oblique shock is distributed between the translational-rotational energy and vibrational energy. The difference in shock angles between different computational settings for the blunt leading edge cases is analogous to that for the sharp leading edge cases， but the difference in the distance from the oblique shock wave to the wall between different computational settings for the blunt leading edge cases is not consistent with that for the sharp leading edge cases. This originates from the influence of the standoff shock wave in front of the blunt leading edge. As to the simulation of oblique shock under freestream condition， if molecular vibrational energy is considered but thermal nonequilibrium is not considered （for example， thermally perfect gas model， one temperature model which takes air reaction into account， etc.）， the resultant error of the shock angle can be even larger than that of calorically perfect gas model.