Characteristics of Separation-Bubble Formation on Finite Circular Cylinder in Critical Transition Range

Yi Hui Lai, Jiun Jih Miau, Guang Ting Zhung, Ming Che Tsai, Ji Ci Wu

Research output: Contribution to journalArticlepeer-review


Experiments were conducted for three finite circular cylinder models for which the aspect ratios were two, three and four, respectively, in the critical transition range. Oil-film flow visualization was performed at Reynolds numbers at the initiation of the critical transition range, which unveiled the three-dimensionality and nonstationarity of multiple separation lines on each of the model surfaces due to intermittent formation of a separation bubble. Moreover, based on the time-averaged pressure coefficients obtained at three heights on each of the models, it was seen that the symmetry of flow varied with Reynolds number. A modified peak–valley method was proposed to identify the intermittent events of separation-bubble formation. By this method, pronounced variations in the realtime signals due to intermittent formation of the separation bubble were identified, which were referred as to the characteristic events. Interesting findings included that the average normalized timescales of the characteristic events fell within 0.1 and 0.6, whereas the average normalized timescales obtained from the real-time traces of the lift coefficient were mostly around 0.08. The difference between these is discussed in this paper.

Original languageEnglish
Pages (from-to)4468-4484
Number of pages17
JournalAIAA journal
Issue number10
Publication statusPublished - 2023 Oct

All Science Journal Classification (ASJC) codes

  • Aerospace Engineering


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