本實驗在微小的測試環境下，以熱線風速計偵測壓縮空氣流經圓柱鈍體後方渦旋逸放的頻率，推導出雷諾數(Re) 與史卓荷數(St) 之關係。預期能利用有效雷諾數的概念，探討加熱圓柱流場的Re-St 關係，將25℃、50℃、100℃、150℃、200℃時的臨界雷諾數回歸成有效臨界雷諾數，導出Re 之分母---空氣黏度，以後便能以此不同環境溫度所對應之空氣黏度方程式，於各式環境下量得空氣的黏度。但因為在實驗中碰到了量測精度的限制，所以這個部份只有做現象的探討，並由觀測渦流逸放頻率發現到加熱圓柱確實可有效地穩定流場。未來也將會提高量測的精度，以期望能達到辨識氣體的效果。;The purpose of this experiment is to measure the vortex-shedding frequency while the compressed air flow over a cylinder by hot-wire anemometer and all of the experiment is set up at the small testing environment. By this way, we can find out the relationship of Reynolds number and Strouhal number. We expect that research the relationship between Re and St while flow over a heated cylinder by using the concept of effective Reynolds number. We can get the effective Re by curving fitting the critical Re at 25℃、50℃、100℃、150℃、200℃each and derive out the viscosity of the air. After this, then we can measure the viscosity of the air everywhere after knowing the viscosity with respect to the specific temperature. We only discuss the phenomena at this part, because the limitation of the accuracy of the instrument. We also observe that a heated cylinder can stabilize the flow field effectively by the vortex-shedding frequency. We are going to enhance the accuracy of the instrument and fulfill the gas identification.
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