本研究乃應用風洞實驗來探討二維方柱及平板位於均勻流與定剪力流中的渦流逸散現象，實驗中使用定溫式熱線測速儀來量測柱體後方之速度分佈及利用頻譜分析找出渦漩逸散頻率，並以二維探針為參考訊號，作為相位平均法的基準，以相位平均法來分析尾流之紊流速度場，進而推求出尾流區之渦度場。實驗結果顯示(1) 剪力流流況下所量得之史徹荷數St均較均勻流小。；(2) 流體流經柱體與平板後會在其後方形成捲增現象，紊流動能在柱體與平板後方迴流區一帶最大，而隨下游距離遞增紊流動能愈不明顯。此現象與縱、橫向紊流強度及紊流消散率有相同的趨勢。；(3)渦度隨時間而做週期性的變化，但會隨下游距離而逐漸減弱；(4)上下渦流的渦度差異遠大於迫近流之渦度，原起於流場中非線性因素放大迫近流之渦度。最後，本研究之結果可增進吾人對非均勻流中柱體及平板尾流之流場機制的瞭解。 This study employed wind tunnel experiment to investigate the wake flows behind a flat plate and a square cylinder placed in constant shear flow. The experiments were conducted in large-scale wind tunnel. The turbulent velocity, kinetic energy, dissipation rate and vorticity were measured by a two-dimensional split-film anemometer. The measured velocity and vorticity distribution were also analyzed by a phase-average technique. The experimental results revealed that the turbulence intensity, Reynolds stress, turbulent kinetic energy and vorticity all have asymmetric distribution in the wake flow. The difference between the upper and lower vorticity is larger than the upstream vorticity. Also, the peak vorticity has a periodic variation, but decays as the downstream distance increases
