Dissipative small-scale actuation of a turbulent shear layer
Dissipative small-scale actuation of a turbulent shear layer
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湍流剪切层的耗散小尺度驱动
DOI：
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发表时间：
2010
影响因子：
3.7
通讯作者：
A. Glezer
中科院分区：
文献类型：
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作者：
B. Vukasinovic;Z. Rusak;A. Glezer
实验研究了小尺度耗散流体驱动对后台阶下游湍流剪切层中大尺度和小尺度运动演化的影响。驱动是通过调制的涡通量进入剪切层的频率，大大高于通常在近场放大的频率，并具有深远的影响层内的涡结构的演变。具体而言，有一个强大的宽带增加的小尺度运动的能量和几乎均匀的大尺度运动的能量减少，这对应于最放大的不稳定模式的基流。强迫剪切层的近场有三个不同的区域。第一个区域（x/θ0 < 50）由湍流动能的产生和耗散以及剪切层横流宽度的显著增加所支配。在第二个区域（50 < x/θ0 < 300），这些量的流向变化率变得与非强迫流中的相应变化率相似，尽管它们的大小有很大的不同。最后，在第三个区域（x/θ0 > 350），剪切层的无粘不稳定性重新出现，可以说是“新的”基线流。
The effects of small-scale dissipative fluidic actuation on the evolution of large- and small-scale motions in a turbulent shear layer downstream of a backward-facing step are investigated experimentally. Actuation is applied by modulation of the vorticity flux into the shear layer at frequencies that are substantially higher than the frequencies that are typically amplified in the near field, and has a profound effect on the evolution of the vortical structures within the layer. Specifically, there is a strong broadband increase in the energy of the small-scale motions and a nearly uniform decrease in the energy of the large-scale motions which correspond to the most amplified unstable modes of the base flow. The near field of the forced shear layer has three distinct domains. The first domain (x/θ0 < 50) is dominated by significant concomitant increases in the production and dissipation of turbulent kinetic energy and in the shear layer cross-stream width. In the second domain (50 < x/θ0 < 300), the streamwise rates of change of these quantities become similar to the corresponding rates in the unforced flow although their magnitudes are substantially different. Finally, in the third domain (x/θ0 > 350) the inviscid instability of the shear layer re-emerges in what might be described as a ‘new’ baseline flow.