Experimental Study on Flow Characteristics around Two-Dimensional rtical Plate in Laminar Plane Boundary Layer

• Main Authors: Wu, Chiuan Huang, 吳權晃
• Other Authors: 林 呈
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/99932626962983166499

碩士 === 國立中興大學 === 土木工程學系 === 93 === Fluid encountering a vertical obstacle with large aspect ratio (ex. the vertical embankment, porous fence and net, enclosure, and sound insulation wall) can be considered as a two-dimensional flow field around a vertical plate. The vortex structure around the vertical plate can be related to the non-dimensional boundary layer thickness (δ/H) and the Reynolds number (Re). The purpose of the present study is to investigate the characteristics and dominating parameters of the flow field around the vertical plate. In the condition of laminar boundary layer at low Reynolds numbers, both flow visualization technique and particle image velocimetry (PIV) system were used. The Reynolds number based upon the free stream velocity (U0) and the height of the vertical plate (H) ranges from 75 to 2000. From the qualitative analysis, it is found that the flow structure in front of the vertical plate was influenced mainly by the Reynolds numbers. In the lee of the vertical plate, there are two kinds of vortex structures when δ/H less than 1, and there is one kind when δ/H greater than 1. As from the quantitative analysis, the similarity of shear layer profiles in the lee of the vertical plate is presented. It is found that, using non-dimensional velocity parameter [ (U-Umin) / (Umax-Umin) ] and non-dimensional length parameter [ (y-b) / θ ], the similarity of the shear layer profiles can be obtained for all conditions. Based upon the characteristics of the shear layer and the Reynolds numbers, the flow field can be classified into two regions and four types.