Mechanism of flow instability and transition to turbulence
Mechanism of flow instability and transition to turbulence
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DOI：
10.1016/j.ijnonlinmec.2005.12.002
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发表时间：
2006-05-01
影响因子：
3.2
通讯作者：
Dou, Hua-Shu
中科院分区：
文献类型：
--
作者：
Dou, Hua-Shu
本文提出了壁面剪切流的流动不稳定和湍流转变的新机制。指出主流横向和流向的总能量梯度主导扰动放大或衰减。因此，它们确定了给定初始扰动下不稳定启动和流动转变的临界条件。提出了一种新的表征流动不稳定性的无量纲参数K，其表示为没有能量输入或输出的流动两个方向上的能量梯度之比。建议流动失稳首先发生在K-max位置，这可能是最危险的位置。这一推测得到了Nishioka等人的实验数据的证实。与平面泊肃叶流和管道泊肃叶流的实验数据对比表明，所提出的想法确实有效。研究发现，无论是平面泊肃叶流还是管道泊肃叶流，湍流转变都发生在 K-max 约为 385 的临界值处，低于该临界值时，无论有扰动，都不会发生湍流。更多研究表明，该理论对于 K-max 临界值约为 370 的平面 Couette 流也有效。(c) 2006 Elsevier Ltd. 保留所有权利。
In this paper, a new mechanism of flow instability and turbulence transition is proposed for wall bounded shear flows. It is stated that the total energy gradient in the transverse direction and that in the streamwise direction of the main flow dominate the disturbance amplification or decay. Thus, they determine the critical condition of instability initiation and flow transition under given initial disturbance. A new dimensionless parameter K for characterizing flow instability is proposed which is expressed as the ratio of the energy gradients in the two directions for the flow without energy input or output. It is suggested that flow instability should first occur at the position of K-max which may be the most dangerous position. This speculation is confirmed by Nishioka et al.'s experimental data. Comparison with experimental data for plane Poiseuille flow and pipe Poiseuille flow indicates that the proposed idea is really valid. It is found that the turbulence transition takes place at a critical value of K-max of about 385 for both plane Poiseuille flow and pipe Poiseuille flow, below which no turbulence will occur regardless the disturbance. More studies show that the theory is also valid for plane Couette flows which holds a critical value of K-max of about 370. (c) 2006 Elsevier Ltd. All rights reserved.