Self-sustained oscillations and vortex shedding in backward-facing step flows: Simulation and linear instability analysis
Self-sustained oscillations and vortex shedding in backward-facing step flows: Simulation and linear instability analysis
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DOI：
10.1063/1.1773091
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发表时间：
2004-07
影响因子：
4.6
通讯作者：
D. Wee;Tongxun Yi;A. Annaswamy;A. Ghoniem
中科院分区：
文献类型：
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作者：
D. Wee;Tongxun Yi;A. Annaswamy;A. Ghoniem
通过线性不稳定性分析，研究了在ST=O(0.1)处的自持续振荡的起源，这种振荡在后向台阶流中已被广泛报道。基于对回流中观测到的一组时间平均速度剖面的局部稳定性分析进行的参数研究表明，绝对模式的频率主要由剪切层厚度决定，绝对模式的增长速度由回流量控制。考虑到实际流动中已知的局部速度剖面的流向变化，这意味着振荡很可能发生在回流区的中部，那里的回流足够强，剪切层厚度与台阶高度相当。由于剪切层厚度受台阶高度的限制，相应的频率被确定为ST=O(0.1)。为了验证这一假设，从二维数值S获得的平均速度剖面.
Linear instability analysis was performed to investigate the origin of the self-sustained oscillations, at St=O(0.1), which have been widely reported in backward-facing step flows. Parametric studies, based on local stability analysis of a family of time-average velocity profiles modeling those observed in recirculating flows, show that the frequency of the absolute mode is determined primarily by the shear layer thickness, and the growth rate of the absolute mode is controlled by the amount of backflow. Given the known streamwise variation of the local velocity profile in the actual flow, this implies that the oscillations are likely to be generated at the middle of the recirculation zone, where the backflow is sufficiently strong, and shear layer thickness is comparable to the step height. The corresponding frequency is determined to be St=O(0.1), because the shear layer thickness is bounded by the step height. To verify this hypothesis, mean velocity profiles obtained from a two-dimensional numerical s...