本實驗以微小圓柱當作人為激擾方式，期望能夠影響平面噴流的流場結構進而增加其擴散與混合特性，實驗噴流出口速度固定為10m/s，此速度相對於噴流出口高度的雷諾數為7.792×10^3，本研究以熱線實驗量測法測量順時速度與平均速度，數據分析後即能觀察平面噴流的渦流結構發展與擴散特性演變，此微小圓柱尺寸為4mm足以完全包含於勢流核當中，與較早期的大件撞擊物體不同，所以預期有不同的結果。撞擊圓柱激擾實驗的實驗變數為不同的撞擊長度：近場區撞擊的撞擊長度= 2H、接近勢流核終點的撞擊長度= 4.5H、以及遠場區撞擊的撞擊長度= 7H。
由平均速度分析來比較自然噴流與撞擊噴流的不同，可以看出在Xcy= 2H 和 4.5H 的速度提早下降且擾動速度提早上升，表示流場近場區域在圓柱的加入之後會提前結束並且進入噴流與尾流的交互影響區域。
在擴散特性分析當中本研究以動量厚度、體積流率、剪流層厚度為比較依據，很明顯地如果圓柱位於勢流核內將能夠有效地增加噴流的擴散特性，總和來說，以圓柱激擾的方式必須要將圓柱放置於勢流核當中，也可推論圓柱的導入對噴流近場區的擴散特性有提升效果，而對於噴流遠場區則沒有益處。
渦流結構與渦流匯聚現象可從頻譜分析當中推測，實驗結果當中的頻譜分析是由快速傅立葉轉換計算而來。自然噴流的頻譜分析中可以看出基本頻率為535Hz，大約在x⁄H=5時半諧頻率(subharmonic frequency=267Hz)的能量超過基本頻率能量，即可推測在x⁄H=5時渦流匯聚。三組不同的撞擊長度實驗皆能發現：共振頻率不同於自然噴流基本頻率535HZ，而轉換為新的共振頻率450Hz，而此共振頻率接近於流過圓柱的尾流頻率，此結果與早期較大圓柱的結果是不同的。

In this study, the evolution of the coherent structures and the spreading characteristics of a small cylinder impinging plane jet are investigated experimentally by means of hot-wire measurements. Throughout the experiments, the jet exit velocity is fixed at 10 m/sec, and the Reynolds number corresponding to the nozzle width is 7.792×10^3. There are three different impinging length cases: (1) the impinging length of 2H for the near-field impingement, (2) 4.5H for the end-of-potential-core impingement, and (3) 7H for the far-field impingement. The aim of this report is to compare the improvement of those three impingement cases. Mean velocity measurement and FFT(Fast Fourier Transform) spectral analysis are applied to interpret the the dynamics of coherent structures.
The results indicated that the existence of the cylinder in the jet flow truly changed the jet flow. After comparing the spreading characteristics between three different impinging length condition. The near-field impingement case and the end-of-potential-core impingement case have better improvement to spreading characteristics. Otherwise, the spectral analysis results also proved the feedback mechanism which mentioned by Ho and Nosseir.

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