本研究以探討不同縫寬之開縫圓柱在均勻流下之渦流溢放現象，並且進一步探討自由紊流擾動對其之影響。實驗分成兩部分，第一部分是在水槽中利用質點影像測速儀(PIV)以非侵入方式觀測在不同縫寬下開縫圓柱流場之變化，並探討在何種縫寬下其穩定性最高。第二部分則是在風洞中利用熱線(Hot-wire)測速儀量測紊流強度對開縫圓柱之影響，利用在開縫圓柱模型上游處架設網格，改變自由流之紊流擾動結構，討論其中渦流溢放頻率之非定常之行為。
PIV實驗結果發現，雷諾數介於2.8×10^3至1.3×10^4時，縫寬越寬渦流溢放頻率相對提高。在雷諾數為5.5×10^3時，發現開縫圓柱縫寬之大小對渦形成長度影響不大，開縫圓柱渦形成長度大約0.9d。利用相位平均方法，得到開縫圓柱在各個周期特定時間之渦流溢放平均流線圖，從流線圖中可以發現到開縫圓柱尾流的渦流溢放過程和圓柱有些許的差異。
風洞實驗結果發現，在均勻流場中，雷諾數介於1.5×10^4至8.5×10^4，透過渦流溢放信號品質分析與線性誤差分析結果發現，s/d=0.1開縫圓柱穩定性最佳。在紊流場中，雷諾數介於1.5×10^4至4.0×10^4時，圓柱與開縫圓柱之St值均會受到紊流強度影響，紊流強度越高St值也越高，在不同紊流強度下，透過渦流溢放信號品質分析與線性誤差分析結果發現，仍是s/d=0.1開縫圓柱穩定性最佳。

Experiments were carried out in a low-speed wind tunnel and a water channel with emphasis on the impact of the slit width on the quality of the vortex shedding signal measured. For the experiments made in water channel, the techniques of Particle Image Velocimetry(PIV) was employed. For the experiments made in wind tunnel, the techniques of constant temperature hot-wire anemometer was employed. In addition, square-meshed grids were used to produce turbulent-flow field in the wind tunnel.
The water channel experiments were carried out at Reynolds numbers in a range of 2.8×10^3-1.3×10^4 for the cylinders of s/d=0.1,0.15,0.2 and 0.25. It was found that the vortex shedding frequency measured is increased with the slit width. At the Reynolds number 5.5×10^3, the vortex formation region of a slit circular cylinder is found to be about x/d=0.9. Moreover, by a phase-averaging method the wake flow pattern of a slit circular cylinder was obtained and compared with that of a circular cylinder.
The wind tunnel experiments were carried out at Reynolds numbers in a range of 1.5×10^4-8.5×10^4. For smooth flow, the vortex shedding signals quality of the slit circular cylinder of s/d=0.1 was found to be the best. And, relation of the Strouhal number against the Reynolds number was also found to be the most linear.
Further efforts were made to examine the effect of free-stream turbulence at high intensity on flow past a slit circular cylinder. The Reynolds number was varied from 1.5×10^4-4.0×10^4. In the turbulent flow, Strouhal number is increased as gets higher turbulence intensity. By examining the data obtained with the circular and slit circular cylinders under the flow conditions of different turbulence intensities, the quality of the vortex shedding signals of s/d=0.1 was found to be the best. Meanwhile the Strouhal number against the Reynolds number was found to be the most linear.

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