Computational fluid dynamics simulations are performed to complement the understanding of shocked gas dynamics from the experiments conducted in Electric Arc Shock Tube facility at NASA Ames Research Center. This analysis focuses on pure nitrogen, where the EAST data is available for shock speeds ranging from 6-11 km/s. An innovative approach is used to compute the shock tube flow evolution in a time-accurate manner where the governing equations are solved in a moving-frame of reference using active shock-tracking. The numerically simulated shock front attains a near-constant speed soon after it is fully formed (i.e., after ten tube-diameters of shock travel) beyond which the post-shock gas properties change relatively slowly. The post-shock gas dynamics are dominated by dissociation at lower speeds, whereas higher shock speeds show increasing degrees of ionization up to 10-15 cm behind the shock. Post-shock electron number densities have been previously reported and show above equilibrium values for shock speeds less than 10 km/s. While there are differences between the two due to the modeling assumptions and the simplifications of the experimental facility made in the numerical modeling, the CFD predicted gas behavior shows a good qualitative match with EAST electron number density data. The analyses provide deeper insight into the shocked gas behavior for a range of test conditions.
展开▼
机译：在NASA Ames研究中心的电弧冲击管设施中进行的实验中，进行了计算流体动力学模拟，以补充对冲击气体动力学的理解。该分析着重于纯氮，其中EAST数据可用于6-11 km / s的冲击速度。一种创新的方法用于以时间精确的方式计算激波管的流量演变，其中使用主动激波跟踪在参考运动框架中求解控制方程。数值模拟的激波锋形成后不久（即在激波行进十个管径之后）很快就达到了接近恒定的速度，超过此速度后，激波后气体的特性变化相对较慢。震荡后的气体动力学以较低的速度解离为主导，而较高的震荡速度则显示出在震荡后直至10-15 cm处的电离度增加。先前已经报道了电击后的电子数密度，并且对于小于10 km / s的冲击速度，其显示出高于平衡值的值。尽管由于建模假设和数值建模中实验设备的简化而使两者之间存在差异，但CFD预测的气体行为与EAST电子数密度数据显示出良好的定性匹配。这些分析为各种测试条件下的冲击气体行为提供了更深入的了解。
展开▼
