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首页> 外文期刊>American journal of applied sciences >Direct Shocks in Vibrationally Nonequilibrium Diatomic Gases at Various Distances from Critical Cross-Section of Nozzle
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Direct Shocks in Vibrationally Nonequilibrium Diatomic Gases at Various Distances from Critical Cross-Section of Nozzle

机译：距喷嘴临界截面不同距离的振动非平衡双原子气体中的直接冲击

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The high-temperature diatomic gas flows are considered in expanding nozzles under the conditions of a disturbance of the equilibrium distribution over vibrational levels of the molecules. The investigation of such flows is bound up with the problem of the inversion of the vibrational populations in the active mediums of molecular lasers. Under diverse values of the pressure overfall on coming out of the nozzle the shock waves can arise at various distances from critical cross-section. Under these conditions the research of the molecular distributions over vibrational levels behind such shocks acquires special significance. Relaxation processes behind a shock-wave front in a vibrationally nonequilibrium gas have been analyzed previously using differential equations for the vibrational populations. In our paper a shock wave is modeled by a thin transient layer between two vibrationally nonequilibrium quasi-stationary states. Generalized conditions of dynamic consistency are derived. The methods of kinetic theory are used. This approach does not allow one to determine the vibrational populations behind a shock wave at various distances from its front. However, it enables one to find the velocity of the gas, the total number of molecules in unit volume, the gas temperature and the temperature, called by Treanor the temperature of the 1st vibrational level, directly behind a shock wave (outside the relaxation zone). The knowledge of these values allows one to determine all parameters of interest using the kinetic theory methods. An advantage of this approach is that the considerably less number of equations is used and the need to know the probabilities of different vibrational transitions is eliminated. Earlier it was shown that the inversion of vibrational populations decreases when the flows pass through a shock wave. In present paper we note two competing factors. The further direct shock is from critical cross-section of the nozzle, the more the nonequilibrium degree of vibrational distributions and the inversion of vibrational populations are. In connection with that the intensity of a shock wave increases. It leads to a decrease of the vibrational nonequilibrium and the inversion of vibrational populations.
机译：考虑到在分子振动水平上平衡分布受到干扰的条件下，在膨胀喷嘴中考虑了高温双原子气流。这种流动的研究与分子激光器的活性介质中的振动种群的反转问题有关。在从喷嘴出来的压力溢出的不同值下，冲击波会在距临界横截面的不同距离处产生。在这些条件下，研究这种冲击背后的振动水平上的分子分布具有特殊的意义。先前已使用振动群的微分方程分析了振动非平衡气体中冲击波前沿后面的松弛过程。在我们的论文中，冲击波由两个振动非平衡准平稳状态之间的薄过渡层建模。导出了动态一致性的一般条件。使用动力学理论的方法。这种方法不允许人们确定在与冲击波不同距离的冲击波后面的振动分布。但是，它使人们能够找到气体的速度，单位体积中的分子总数，气体温度以及直接在冲击波后面（弛豫区之外）的第一个振动能级的温度（由Treanor称为温度）。 ）。这些值的知识使人们能够使用动力学理论方法确定所有感兴趣的参数。这种方法的优点是使用的方程式数量少得多，并且消除了了解不同振动转变概率的需要。较早的研究表明，当流动通过冲击波时，振动总体的反演减小。在本文中，我们注意到两个竞争因素。来自喷嘴的临界横截面的直接冲击越多，振动分布的不平衡度和振动总体的倒转就越大。与此相关，冲击波的强度增加。它导致振动不平衡的减少和振动分布的反转。

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