Global frequency selection in the observed time-mean wakes of circular cylinders
Global frequency selection in the observed time-mean wakes of circular cylinders
复制标题
观测到的圆柱体时间平均尾流的全局频率选择
DOI：
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复制
发表时间：
2008
影响因子：
3.7
通讯作者：
K. Hourigan
中科院分区：
文献类型：
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作者：
M. Khor;J. Sheridan;M. Thompson;K. Hourigan
在600和4600之间的中等雷诺数下，对圆柱近尾流中跨中的时间平均速度剖面进行了观测，远远超过了尾流变为三维的雷诺数约200。测量的配置文件被认为是相当准确地表示由一个家庭的功能配置文件与已知的线性不稳定特性。然后，使用函数分布确定作为尾流位置的函数的复杂不稳定性频率。在一般情况下，近尾流经历了从对流到绝对不稳定的过渡，下游的距离过渡点被发现增加的雷诺数范围内调查。一个重要的对流不稳定区域的出现与已知的Bloor-Gerrard涡的出现是一致的。尾流不稳定性的选定频率由鞍点准则确定;发现Bénard-von Kármán涡脱落的Strouhal数与文献中的值比较好。
Observations have been made of the time-mean velocity profile at midspan in the near-wake of circular cylinders at moderate Reynolds numbers between 600 and 4600, well beyond the Reynolds number of approximately 200 at which the wake becomes three-dimensional. The measured profiles are found to be represented quite accurately by a family of function profiles with known linear instability characteristics. The complex instability frequency is then determined as a function of wake position, using the function profiles. In general, the near wake undergoes a transition from convective to absolute instability; the distance downstream to the point of transition is found to increase over the Reynolds number range investigated. The emergence of a significant region of convective instability is consistent with the known appearance of Bloor–Gerrard vortices. The selected frequency of the wake instability is determined by the saddle-point criterion; the Strouhal numbers for Bénard–von Kármán vortex shedding are found to compare well with the values in the literature.