The transient start of supersonic jets
The transient start of supersonic jets
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DOI：
10.1017/s0022112007004715
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发表时间：
2006-11
影响因子：
3.7
通讯作者：
M. Radulescu;C. Law
中科院分区：
文献类型：
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作者：
M. Radulescu;C. Law
本研究研究了高度欠膨胀狭缝和圆形射流的初始瞬态流体动力学演化。针对扩散通量消失的喷头处温度、压力和密度的时间演化，导出了封闭式解析相似解，概括了使用 Chernyi 的高超音速流边界层方法的先前 Chekmarev 模型。还进行了二维数值模拟，以研究初始阶段在约 1000 个孔口半径的距离内的流场。模拟中使用的参数对应于加压氢气释放到环境空气中，压力比在大约 100 到 1000 之间变化。模拟证实了理论上推导的相似定律，并表明射流头部在早期阶段是层流，而在射流侧面建立了复杂的声学不稳定性，涉及涡环内的冲击相互作用，这与之前的实验结果非常吻合。在射流瞬态建立过程中，对于狭缝射流和圆形射流获得的当前模型、数值模拟和先前的实验结果之间存在非常好的一致性。还导出了喷射头处减速密度梯度的瑞利-泰勒不稳定性的标准，以及解决在反应气体突然释放期间形成的不稳定膨胀扩散层的点火的模型的公式。
This study investigates the initial transient hydrodynamic evolution of highly under-expanded slit and round jets. A closed-form analytic similarity solution is derived for the temporal evolution of temperature, pressure and density at the jet head for vanishing diffusive fluxes, generalizing a previous model of Chekmarev using Chernyi's boundary-layer method for hypersonic flows. Two-dimensional numerical simulations were also performed to investigate the flow field during the initial stages over distances of ~ 1000 orifice radii. The parameters used in the simulations correspond to the release of pressurized hydrogen gas into ambient air, with pressure ratios varying between approximately 100 and 1000. The simulations confirm the similarity laws derived theoretically and indicate that the head of the jet is laminar at early stages, while complex acoustic instabilities are established at the sides of the jet, involving shock interactions within the vortex rings, in good agreement with previous experimental findings. Very good agreement is found between the present model, the numerical simulations and previous experimental results obtained for both slit and round jets during the transient establishment of the jet. Criteria for Rayleigh–Taylor instability of the decelerating density gradients at the jet head are also derived, as well as the formulation of a model addressing the ignition of unsteady expanding diffusive layers formed during the sudden release of reactive gases.