本文以粒子影像測速儀(PIV)應用於二維不具壁面效應之平板混合層(mixing layer)風洞之速度量測，並以熱線測速儀的量測結果做為PIV量測之比較基準。
流場實驗條件為固定兩個R值，R=0.6及R=0.4，其分別對應的高速測的自由流速度為15.5(m/s)及17.5(m/s)，低速測的自由流速度為3.78(m/s)及7.39(m/s)。本研究並在高速側加入不同顆粒濃度(∝=0,1,3,5%)之大顆粒(分散相)。為進一步應用於兩相紊流場速度PIV量測，本研究加入同材質之兩種粒徑分佈之二氧化矽粉末，其中連續相之平均粒徑為3.9μｍ，分散相之平均粒徑為58μｍ。由於影像上的粒徑尺寸差距小，無法使用影像大小的中值濾波器(median mask)來區分，因此只能運用灰階的門檻值來進行篩選。我們在此採用不同的灰階值(gray level) ，來區分同一張影像中的連續相(carrier-phase)與分散相(dispersed-phase)顆粒。此外，連續相的速度計算仍沿用PIV演算法，但分散相的速度計算則使用PTV演算法，進行氣固兩相紊流速度之量測計算。
由上述實驗中，我們得到最佳灰階門檻值為 ，為了進一步確定PTV量測分散相速度的可靠性，我們分別於不同分散相濃度條件下，測試所需之樣本數目方能具有統計意義。而收集數目又與碰撞頻率密切相關，收集數目必須隨著碰撞頻率增加而增加，且隨著顆粒濃度增大而增加收集數目。本實驗拍攝張數為兩萬張(一萬組)數據，在α=1%的情況下所有的數據都是可行的；在α=3%下只有某些數據可行；而當α=5%時即不可行。

This thesis studies the application of Particle Image Velocimetry (PIV) to the measurements of the instantaneous velocity in a two-dimensional, mixing-layer wind tunnel where there is no confined boundary layer. These measurements are compared with those made with a hot-wire anemometry.
The velocity ratios (R) between high- and low-speed stream are maintained at R=0.6 and R=0.4, corresponding to the two speed pairs (15.5m/s, 3.78m/s) and (17.5m/s, 7.39m/s), respectively. Large particles (dispersed phase) with various concentrations (∝=0,1,3,5%) are introduced to the high-speed free stream. For the study of the application of PIV to the measurements of velocity field of two-phase turbulent flow, two groups of powders with different sizes are employed: the small one represents as the tracer (seeding) particles, while the large one represent the dispersed phase. The size of smaller particles (carrier phase) is 3.9μm in average, while the size of large ones (dispersed phase) is 58μm in average. However, the difference in the size between the carrier phase and dispersed phase is too small to be distinguished by using a median mask for image size. Only the threshold in gray level is, thus, employed to discriminate the image patterns of the carrier phase (tracers) and the dispersed phase in the turbulent particle-laden mixing layer. The PTV algorithm is applied to obtain the velocity of the dispersed phase, while the PIV algorithm is applied to obtain the velocity of the carrier phase .
To ensure the reliability of flow velocity in dispersed phase obtained by PTV, under the optimal gray-level threshold , a series of tests of the required sample amount under different dispersed phase concentrations are examined to check whether or not their results are statistically meaningful. It is known that the required sample amount is dependent on the inter-particle collision rate. As a result, the required sample amount is increased along with the particle loading ratio. Twenty thousand images, corresponding to ten thousand sets of raw data, are shot. It shows that this algorithm works well asα=1%, moderately asα=3%, and poorly asα=5% in this study .

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