水利学报2016，Vol.47Issue(2)：158-164,7.DOI:10.13243/j.cnki.slxb.20150528
明渠柱体上游马蹄涡的运动学特征研究
Kinematic characteristics of horseshoe vortex upstream of circular cylinders in open channel flow
摘要
Abstract
To investigate the kinematic characteristics of horseshoe vortex upstream of cylinders, the swirl⁃ing strength method is introduced to identify horseshoe vortices, and a method of fitting the local velocity field with an elliptic vortex are proposed to characterize these vortices. The elliptic vortex is constructed by overlapping the Oseen vortex with an inclined unidirectional shear flow. The proposed methods were used to investigate the time-averaged horseshoe vortex upstream of a circular cylinder in open channel flow. The time averaged horseshoe vortex is captured by averaging instantaneous velocity fields measured with PIV. The results show that, in flows with cylinder Reynolds number larger than 104, the position of horseshoe vortex is unchanged while the upstream separation point moves downstream slowly. The distances from the vortex center to the cylinder axis and the bed are 0.67D and 0.06D, respectively, with D being the cylin⁃der diameter. Comparing with those in open channel flows,the horseshoe vortex and separation point in tur⁃bulent boundary layers are further upstream. With the increasing of cylinder Reynolds number, the horse⁃shoe vortex strengthens itself but keeps the size unchanged, results in increasing shear stress on the bed. The dependence of vortex-induced shear stress with the flow strength indicates that it is physically reason⁃able to formulate equations for local scour based on the kinematic characteristics of horseshoe vortex.关键词
柱体绕流/马蹄涡/特征提取/运动学特征/粒子图像测速Key words
flow around cylinder/horseshoe vortex/characteristic extraction/kinematic characteristics/par-ticle image velocimetry分类
水利科学引用本文复制引用
陈启刚,齐梅兰,李金钊..明渠柱体上游马蹄涡的运动学特征研究[J].水利学报,2016,47(2):158-164,7.基金项目
中国博士后科学基金项目（2015M570031）；国家自然科学基金项目 （）
