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首页> 外文期刊>Experiments in Fluids: Experimental Methods and Their Applications to Fluid Flow >Investigation of coherent structures generated by acoustic tube in turbulent flow separation control
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Investigation of coherent structures generated by acoustic tube in turbulent flow separation control

机译：湍流分离控制中声管产生相干结构的研究

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摘要

An acoustic tube was designed in order to control the turbulent flow separation downstream of a backward-facing step. The Reynolds number based on the freestream velocity and the step height was Re-h = 2.0 x 10(4). As an active flow control device, the acoustic tube generated periodic pressure perturbations at a frequency of f(a) = 100 Hz, which was close to the most amplified frequency of the shedding instability of the turbulent shear layer. Spanwise vortices rolled up due to the perturbations. 2D-2C particle image velocimetry was used to measure separated shear layer and the reattachment area downstream of the BFS. The flow control results show that the acoustic tube can suppress recirculation regions behind the step and reduce the reattachment length by 43.7 %. The roll-up and pairing processes of the vortices lead to an increase in the total Reynolds shear stress. The coherent structures are extracted by proper orthogonal decomposition and represented by two pairs of modes, of which the coherence is analyzed by the corresponding coefficients. Both the primary and secondary series of vortices are reconstructed as traveling waves with the fundamental frequency f(a) and the overtone frequency 2f(a), respectively.
机译：为了控制向后步骤下游的湍流分离，设计了声管。基于自由流速度和台阶高度的雷诺数为Re-h = 2.0 x 10（4）。作为一种主动流量控制设备，声管在f（a）= 100 Hz的频率下产生周期性的压力扰动，该扰动与湍流剪切层脱落不稳定性的最大放大频率接近。由于扰动，水平方向的涡旋卷起。使用2D-2C粒子图像测速仪测量分离的剪切层和BFS下游的重新附着区域。流量控制结果表明，声管可以抑制台阶后面的再循环区域，并减少重新安装长度43.7％。涡旋的卷起和配对过程导致总雷诺剪切应力的增加。通过适当的正交分解提取相干结构，并用两对模式表示，并用相应的系数分析其相干性。初级涡旋序列和次级涡旋序列均被重构为分别具有基本频率f（a）和泛音频率2f（a）的行波。

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