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|標題:||Characteristics of horseshoe vortex system near a vertical plate-base plate juncture|
|期刊/報告no：:||Experimental Thermal and Fluid Science, Volume 27, Issue 1, Page(s) 25-46.|
|摘要:||In-depth study of horseshoe vortex flows, near the juncture of a vertical plate and a base plate, is performed using flow visualization technique, fiber laser Doppler velocimetry and particle image velocimetry systems. The flow patterns are classified into four major categories while the Reynolds number, based on the free stream velocity and the width of vertical plate, varies from 400 to I 1000, and the height-to-width ratio changes from 0.5 to 4.0. These four major categories are defined as (1) steady vortex system, (2) periodic oscillation vortex system with small displacement, (3) periodic breakaway vortex system, and (4) turbulent-like vortex system. In the categories of periodic oscillation vortex system with small displacement and periodic breakaway vortex system, the Strouhal number increases with increasing Reynolds number if the width of the vertical plate is employed in the non-dimensional parameters. However, when the uniform flow speed and the height of vertical plate are maintained the same, the frequency of periodic oscillation and periodic breakaway vortex systems do not increase with the increasing width. This indicates that the width of vertical plate is not a characteristic length that affects the frequency of the periodic motion of the horseshoe vortex system. Conversely, the Strouhal numbers, based on the boundary layer thickness, change from 0.0611 to 0.0896 and are found to be nearly independent of the Reynolds numbers. This clearly reveals that the boundary layer thickness is an important length scale that controls the frequency of the horseshoe vortex system. (C) 2002 Elsevier Science Inc. All rights reserved.|
|Appears in Collections:||土木工程學系所|
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