應用PIV與流場可視化技術於近一平板之圓柱近域尾流流場特性探討

Abstract

本文旨在以精密非接觸之實驗方式，對於雷諾數為780與100之情況下，探討平板對圓柱尾流流場特性之影響。實驗中運用流場可視化法對流場特性做定性上之實驗觀察，並配合質點影像測速儀( PIV )將流場量化量測，提供研究做數據之分析，並輔以精密量測儀器光纖雷射杜普勒測速儀( FLDV )對流場之運動特性及頻率進行詳細量測。研究中改變雷諾數( Re )、模型與平板之間距( G/D )、邊界層厚度(δ)等因子，以探討當圓柱接近平板之過程中，圓柱尾流在速度場結構上之變化、渦流結構之差異性與渦流釋放頻率之相對應關係以及流場特性上之改變。

The flow characteristics in the near wake of a circular cylinder near a plane boundary were investigated experimentally, using particle image velocimetry (PIV), fiber laser Doppler velocimetry (FLDV), and flow visualization techniques. Fluctuations of velocity and the formation of the vortex in the wake of the circular cylinder were studied in terms of the gap height between cylinder and plane and the thickness of the laminar plane boundary layer. The Strouhal number due to the vortex shedding frequency in the wake of a circular cylinder depend on the combination of the gap height between the cylinder and the plane. Flow visualization experiments revealed the wake structure at various gap heights at Reynolds numbers of 100 and 780.