Experiments on a jet in a crossflow in the low-velocity-ratio regime
Experiments on a jet in a crossflow in the low-velocity-ratio regime
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低速比状态下横流射流实验
DOI：
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发表时间：
2019
影响因子：
3.7
通讯作者：
J. Wesfreid
中科院分区：
文献类型：
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作者：
L. Klotz;K. Gumowski;J. Wesfreid
实验研究了低射流-横流速度比下射流在横流中的发夹不稳定性，流速比为$Rin(0.14,0.75)$，横流雷诺数为$Re_{D}in(260,640)$。通过谱分析，我们将发夹不稳定性的Strouhal数和幅值表征为R和Re_{D}$的函数。我们证明了发夹的动力学是由朗道模型很好地描述的，因此，不稳定性通过Hopf分岔发生，类似于其他流体动力振荡器，如不同钝体后面的尾迹。利用朗道模型，确定了发夹脱落的精确阈值。我们还研究了这种流体动力不稳定性的空间依赖性，它显示了一种全局行为。
The hairpin instability of a jet in a crossflow (JICF) for a low jet-to-crossflow velocity ratio is investigated experimentally for a velocity ratio range of $Rin (0.14,0.75)$ and crossflow Reynolds numbers $Re_{D}in (260,640)$ . From spectral analysis we characterize the Strouhal number and amplitude of the hairpin instability as a function of $R$ and $Re_{D}$ . We demonstrate that the dynamics of the hairpins is well described by the Landau model, and, hence, that the instability occurs through Hopf bifurcation, similarly to other hydrodynamical oscillators such as wake behind different bluff bodies. Using the Landau model, we determine the precise threshold values of hairpin shedding. We also study the spatial dependence of this hydrodynamical instability, which shows a global behaviour.