本研究主要是針對一均勻流經兩並列的旋轉圓柱時，兩圓柱的間隙、旋轉速度對流體流動所造成的影響。透過沉浸邊界法模擬Re=100時兩圓柱在不同的旋轉速度、間隙下流體的流動現象。而圓柱旋轉的方向會使得間隙流呈現減速或加速的現象。數值預測之流場變化以渦度等高線與流線來可視化。在間隙流為減速的案例中，當超過臨界旋轉速度1.8、1.4、1.4和1.3其間隙大小分別為3、1.5、0.7和0.2時，尾流的發展會完全被抑制。在間隙流為在小間隙時尾流的發展會比在大間隙時更早達到穩定得狀態，然而在加速的間隙流時，只有大間距並在高速旋轉的情況下渦旋逸出共有反相、同相、八字形、單一渦旋與完全抑制五種型式。此外，升阻力係數的時序圖也提供來瞭解旋轉圓柱的效應。本研究並計算自相關函數並用於瞭解兩圓柱後渦旋逸出的相關性。

This study aims to investigate a uniform flow past a pair of side-by-side rotating cylinders at the moderate Reynolds number 100. The effects of gap between two cylinders, rotational direction and speed on vortex streets behind cylinders are discussed in this study. A numerical model based on the immersed boundary method is established. The direction of rotational speed results in either a decelerating or an accelerating gap flow. The effects of the decelerating and accelerating gap flow on the vortex streets are studied
as well. Numerical results are visualized using vorticity contours and stream lines. In the case of a decelerating gap flow, vortex sheddings are completely suppressed when the rotational speed is faster than the critical rotational speed which varies with respect to the gap. Nevertheless, the vortex shedding behind cylinders is suppressed in the cases with an accelerating gap flow at a fast rotation speed and in a big gap. The mode of vortex shedding varies with respect to gap and rotational speed in the decelerating and accelerating gap flow. In general there are five modes, anti-phase, in-phase, flip-flop,
single vortex shedding, suppressed mode, in the predicted flow fields. Time histories of lift and drag coefficients are provided. To estimate the relationship between two vortex systems behind cylinders, the autocorrelation function is calculated. Time histories of the autocorrelation function explain how those vortex systems interact with each other.

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