耗散气体中的激波不稳定性
Shock instability in dissipative gases
摘要：
先前的实验已经揭示了热弛豫气体中的冲击波，例如电离、离解和振动激发气体，可以变得不稳定。迄今为止，控制这种不稳定性的机制尚未得到解决。先前对D 'yakov-Kontorovich不稳定性和Bethe-Zel'dovich-Thompson行为的描述无法预测实验观察到的不稳定性。为了解决控制不稳定性的机制，我们研究了冲击波在一个简单的二维耗散硬盘分子模型中的传播。为了解释冲击波结构中从平移自由度到更高模式的能量弛豫，我们允许高于激活阈值的非弹性碰撞。当介质允许有限耗散时，我们发现激波是不稳定的，并在其表面形成独特的高密度非均匀性和对流卷。使用冲击Hugoniot的分析和数值结果，我们表明，DK和BZT不稳定性可以排除。相反，结果表明，在耗散气体的Goldhirsch和Zanetti的集群不稳定性是占主导地位的机制。
英文摘要：
Previous experiments have revealed that shock waves in thermally relaxing gases, such as ionizing, dissociating and vibrationally excited gases, can become unstable. To date, the mechanism controlling this instability has not been resolved. Previous accounts of the D'yakov-Kontorovich instability, and Bethe-Zel'dovich-Thompson behaviour could not predict the experimentally observed instability. To address the mechanism controlling the instability, we study the propagation of shock waves in a simple two-dimensional dissipative hard disk molecular model. To account for the energy relaxation from translational degrees of freedom to higher modes within the shock wave structure, we allow inelastic collisions above an activation threshold. When the medium allows finite dissipation, we find that the shock waves are unstable and form distinctive high density non-uniformities and convective rolls on their surface. Using analytical and numerical results for the shock Hugoniot, we show that both DK and BZT instabilities can be ruled out. Instead, the results suggest that the clustering instability of Goldhirsch and Zanetti in dissipative gases is the dominant mechanism.
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