Subcritical transition to turbulence in a sudden circular pipe expansion
Subcritical transition to turbulence in a sudden circular pipe expansion
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圆形管道突然膨胀时亚临界过渡到湍流
DOI：
10.1017/jfm.2018.421
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发表时间：
2018
影响因子：
3.7
通讯作者：
Tasaka Yuji
中科院分区：
文献类型：
--
作者：
Lebon Benoit;Peixinho Jorge;Ishizaka Shun;Tasaka Yuji
给出了中等雷诺数下圆形突扩管内流动的实验结果。在扩张器上游五个直径处，层流流动受到(恒定)横流射流、吸力或(周期性输入-输出)合成射流的干扰。当扰动超过取决于雷诺数的控制参数的临界值时，在固定轴向位置的扩张器下游形成局部湍流斑块。对于横流射流，湍流斑块的形成与射流平均速度与管内平均速度之比有关。在低速比下，湍流斑块间歇性形成。对于吸力扰动，流动经历了回流区的强烈不对称性，需要较大的速度比才能形成湍流斑块。对于合成射流，波动扰动向湍流斑块的放大及其轴向位置由驱动频率控制。总体而言，这些结果表明，局部湍流斑块的发展存在不同的机制。
The results of experiments on the flow through a circular sudden expansion pipe at moderate Reynolds numbers are presented. At five diameters upstream of the expansion, laminar flow was disturbed by a (constant) cross-flow jet, a suction or a (periodic in–out) synthetic jet from a hole in the wall. When the disturbance exceeded a critical value of the control parameter depending on the Reynolds number, localised turbulent patches formed downstream of the expansion at fixed axial positions. For the cross-flow jet, the onset of turbulent patches is related to the velocity ratio of the mean jet velocity to the mean pipe velocity. At low velocity ratio, turbulent patches formed intermittently. For the suction disturbance, the flow experienced a strong asymmetry of the recirculation region and required a larger velocity ratio before the turbulent patch formed. For the synthetic jet, the amplification of wavy disturbances into turbulent patches and their axial positions are controlled by the driving frequency. Overall, these results suggest the existence of different mechanisms for the development of localised turbulent patches.