三維光纖雷射杜普勒測速系統在明渠紊流流場量測上之應用

Abstract

本實驗首先建立三維光纖雷射杜普勒測速系統（3-D Fiber-Optic Laser Doppler Velocimetry，簡稱FLDV），並據以進行光滑床面之三維明渠紊流流場量測。實驗寬深比介於2.94∼10之間；坡度分別為0.1％及0.3％；福祿數介於0.94∼1.18之間；雷諾數涵蓋9530∼44209之範圍。流場分二維檢測與三維分析討論之。 文中主要分析項目包括：平均速度剖面、紊流強度分佈、雷諾應力分佈及渦度產生項分佈等水力特性。在平均速度分佈方面，分別與壁定理、冪次定理，及李（2000）之雷諾應力模式（RSM，Reynold Stress Model）數值模擬結果作比較。紊流強度分佈及雷諾應力分佈與Nezu、Tracy等前人之研究作比較；渦度產生項則與Tominaga之熱膜實驗結果比較，以研析流場之水力特

A 3-D Fiber-optic Laser Doppler Velocimetry system ( FLDV ) was set up and adopted in this experimental study to investigate the characteristics of the turbulent open channel flow over a smooth boundary. In this study, the aspect ratio varied from 2.94 to 10, the Reynolds number varied from 9530 to 44209, the Froude number ranged from 0.94 to 1.18, and the channel bed slopes of 0.1% and 0.3% were selected. Both two-dimensional and three-dimensional flows were discussed. The measured mean velocity profiles were compared with the law of the wall, the power law and the results of Lee's RSM model. The measured distributions of the turbulence intensities and the Reynolds stress were analyzed and compared with the results of Nezu, and Tracy. The measured distributions of the production term were compared with the hot film measurements of Tominaga .