旋转爆轰中滑移线处尾迹不稳定性的解释
Interpretation of wake instability at slip line in rotating detonation
摘要：
在旋转爆轰流场不稳定性的研究中，爆轰波与斜激波交汇引起的滑移线处的不稳定性是一个普遍关注的问题。采用欧拉方程和氢/空气混合物的7组分8反应有限速率化学反应模型，对二维旋转爆轰进行了数值模拟，深入研究了滑移线处不稳定性的流动机理。结果表明，滑移线处存在明显的尾迹分布，与典型的混合层不同。分析表明，尾流的产生是由爆轰波与斜激波之间的过渡激波引起的。由于尾迹剖面的存在，涡量分布呈现双层布局，不同涡量层的涡量分布有不同的演变。根据滑移线上的速度分布，利用线性稳定性理论进行分析，发现了两种形状和相速度不同的不稳定模态，并利用离散傅里叶变换对数值结果进行了分析，得到了相似的形状分布。涡运动速度的理论预测和模拟结果也基本一致。研究表明，尾流不稳定性是造成混合层不稳定的主要原因，相应的不稳定结构不同于典型混合层的正则结构。
英文摘要：
In studies on instabilities of flowfield in rotating detonation, one of the most common concerns is the instability at the slip line originating from the conjunction of the detonation wave and oblique shock. Using Euler equations associated with 7-species-and-8-reaction finite-rate chemical reaction model of hydrogen/air mixtures, further studies are performed to simulate the 2-D rotating detonation, and the flow mechanism of instability at the slip line is investigated in depth. The results show that the distinct wake profile exists at the slip line, which is different from the typical mixing layer. Analysis indicates that the generation of wake is caused by the transition shock between the detonation wave and oblique shock. Because of the wake profile, the vorticity distribution therein appears in a double-layer layout, and different evolution exist in different vorticity layers. Based on the velocity profile across the slip line, the analysis by the linear stability theory is made, and two unstable modes which have different shape profiles and phase velocities are found. Discrete Fourier transformation is utilized to analyze the numerical results, and similar shape profiles are obtained. A general coincidence in velocity of vortex movement is also attained between the theoretical predictions and simulations. Investigations show that the wake instability is responsible for the unstable mechanism, and corresponding unstable structures differs from the canonical ones in typical mixing layers.
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