| Summary: | 碩士 === 國立中興大學 === 土木工程學系 === 88 === When a laminar boundary layer encounters a bluff obstacle extending from a horizontal bottom, a three-dimensional flow field, so-called laminar horseshoe vortex formed in the junction region. These types of flow fields develop in many real systems, and they have significant consequences. The characteristics of horseshoe vortex system in the junction region of three bluff bodies with different shapes (vertical plate, circular cylinder and rectangular pillar) were studied experimentally. The present study concentrates on steady behavior of horseshoe vortex at low Reynolds number and relatively large boundary layer thickness using particle image velocimetry (PIV), fiber laser Doppler velocimeter (FLDV), and two flow visualization techniques. The range of the Reynolds number Re, based upon the free stream velocity (U0 ) and the width of vertical plate (W), is from 200 to 1200. The purpose of the present study is to provide the qualitative and quantitative properties of the steady state of horseshoe vortex system. The structure of horseshoe vortex was observed at low Reynolds number when flow parameters changed. Detail characteristics of the steady horseshoe vortex behavior including the position of primary vortex core, the position of stagnation point on the model, down-flow velocity profile, and the circulation of primary vortex are quantified and discussed in detail in the present study.
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