本研究分析前端具有1D圓蓋之有限長圓柱的PIV量測資料，分析實驗資料在兩個不同觀測平面(X-Y平面及Y-Z平面)的二維速度場量測結果，雷諾數(ReD)為250、560及1080。
分別觀測比較距離圓柱頂端(X/D = 0)及圓柱軸向(Y/D = 0)近、中、遠的位置，分析九個觀測位置在X-Y與Y-Z平面上的Y方向速度資料，包括平均和瞬時速度資料。
近尾流區(Y/D = -1)的三個觀測點中，圓柱前段觀測點(-1.5, -1, 0)在兩個不同觀測平面上的平均速度差距最為顯著，其餘兩個觀測點則沒有明顯的差距;中間過渡轉換區(Y/D = -3)的三個觀測點，在兩個不同觀測平面上的平均無因次速度差距為0.2 ~ 0.4之間，相較於X-Y平面， Y-Z平面有較大的Y方向速度;遠尾流區(Y/D = -5)的三個觀測點，在兩個不同觀測平面上的平均無因次速度皆很相近，而圓柱前段觀測點(-1.5, -5, 0)的速度最接近自由流流速。
九個觀測點中的兩個觀測點(-1.5, -3, 0)及(-1.5, -5, 0)在兩個不同觀測平面上的瞬時速度資料分佈與常態分佈有明顯的差異， X-Y平面有超過45%的瞬時速度資料集中在[μ-σ, μ]; Y-Z平面的瞬時速度資料多半分佈在兩個特定的區間，超過60%的瞬時速度資料集中在[μ-σ, μ]。
X-Y平面的實驗量測平均速度結果顯示在靠近圓柱頂端及圓柱下方(Y/D = 0 ~ -3)， X方向速度有顯著的速度值， Y方向速度有和自由流方向相反的迴流;數值模擬的平均速度結果則顯示在圓柱下方， Y/D = 0 ~ -2， X方向速度與Y方向速度在空間上都有週期性的改變。
Y-Z平面的實驗量測平均速度結果顯示在圓柱前段， X/D = -1.5， Y方向速度受影響的範圍，在雷諾數(ReD) = 250時，涵蓋Y/D = 0 ~ -6;雷諾數(ReD) = 560時，涵蓋Y/D = 0 ~ -3.5;雷諾數(ReD) = 1080時，涵蓋Y/D = 0 ~ -3， Y方向速度受影響的範圍會隨著雷諾數(ReD)增加而減小;圓柱中、後段X/D = -5.5、-10.5， Y方向速度受影響的範圍皆涵蓋Y/D = 0 ~ -10; Z方向速度在圓柱尾流區域有一至三對速度方向相反且交錯的渦流;
數值模擬的平均速度結果則顯示在圓柱前段， X/D = -1.5， Y方向速度受影響的範圍，在雷諾數(ReD) = 250時，涵蓋Y/D = 0 ~ -5;雷諾數(ReD) = 560時，涵蓋Y/D = 0 ~ -5.5;雷諾數(ReD) = 1080時，涵蓋Y/D = 0 ~ -8;圓柱中、後段X/D = -5.5、-10.5， Y方向速度受影響的範圍，在雷諾數(ReD) = 250時，涵蓋Y/D = 0 ~ -7;雷諾數(ReD) = 560時，涵蓋Y/D = 0 ~ -8;雷諾數(ReD) = 1080時，涵蓋Y/D = 0 ~ -10， Y方向速度受影響的範圍會隨著雷諾數(ReD)增加而增加; Z方向速度在圓柱尾流區域僅有一對速度方向相反的渦流。

In this study, the Particle Image Velocimetry (P.I.V.) measurements of a finite length cylinder with a 1D cap at its tip are used to analyze the velocity data in its wake region.
Two-dimensional PIV measurement results on two different observation planes, X-Y plane and Y-Z plane, are analyzed with Reynolds numbers (ReD) as 250、560 and 1080.
The average and instantaneous Y velocity data are analyzed at nine observation points, which are located away from the cylinder tip (X/D = 0) and the cylinder axial (Y/D = 0) short、middle and long distances respectively.
In the near wake region (Y/D = -1), three observation points are observed, the observation point (-1.5, -1, 0) near the cylinder tip has the most significant non-dimensional average velocity difference between two different observation planes, and the other two observation points are similar between them.
In the transition region (Y/D = -3), three observation points are observed, the non-dimensional average velocity difference between two different observation planes is around 0.05 ~ 0.45, and the Y-Z plane has a greater velocity than that on the X-Y plane.
In the far field wake region (Y/D = -5), three observation points are observed, the non-dimensional average velocity between two different observation planes is similar, and the velocity of the observation point (-1.5, -5, 0) near the cylinder tip is close to the freestream velocity.
Two observation points (-1.5, -3, 0) and (-1.5, -5, 0) among nine observation points, the instantaneous velocity data distributions have significant deviations from the normal distribution on two different observation planes; the X-Y plane has more than 45% of the instantaneous velocity data concentrated in [μ-σ, μ], and the Y-Z plane instantaneous velocity data are mostly distributed in two specific ranges, more than 60% of the instantaneous velocity data concentrated in [μ-σ, μ].
In the X-Y plane, experimental average velocity results near the cylinder tip and during Y/D = 0 ~ -3, show that there is an obvious X-direction velocity component and Y-direction velocity component is opposite to the freestream velocity; numerical simulation average velocity results during Y/D = 0 ~ -2, show that X-direction velocity component and Y-direction velocity component have a periodic change in space.
In the Y-Z plane, experimental average velocity results at X/D = -1.5, show that Y-direction velocity component is reduced in the range of Y/D = 0 ~ -6 as ReD = 250; Y/D = 0 ~ -3.5 as ReD = 560 and Y/D = 0 ~ -3 as ReD = 1080. The influence extent of Y-direction velocity component near the cylinder tip decreases as the Reynolds number (ReD) increases. At X/D = -5.5 and -10.5, Y-direction velocity component is reduced in the range of Y/D = 0 ~ -10 and Z-direction velocity component has one to three pairs of vortices in the middle and far distances away from the cylinder tip.
Numerical simulation average velocity results at X/D = -1.5, show that Y-direction velocity component is reduced in the range of Y/D = 0 ~ -5 as ReD = 250; Y/D = 0 ~ -5.5 as ReD = 560 and Y/D = 0 ~ -8 as ReD = 1080 near the cylinder tip. At X/D = -5.5 and -10.5, Y-direction velocity component is reduced in the range of Y/D = 0 ~ -7 as ReD = 250; Y/D = 0 ~ -8 as ReD = 560 and Y/D = 0 ~ -10 as ReD = 1080. The influence extent of Y-direction velocity component in the near、middle and far distances away from the cylinder tip increases as the Reynolds number (ReD) increases, Z-direction velocity component has only a pair of vortices in the near、middle and far distances away from the cylinder tip.

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