Investigation of flow structure around a horizontal cylinder at different elevations in shallow water
Investigation of flow structure around a horizontal cylinder at different elevations in shallow water
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DOI：
10.1016/j.oceaneng.2014.12.033
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发表时间：
2015-03
影响因子：
5
通讯作者：
N. F. Ozdil;H. Akilli
中科院分区：
文献类型：
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作者：
N. F. Ozdil;H. Akilli
研究了浅水中水平圆柱绕流的流动特性。实验中圆柱直径、浅水高度和自由流流速分别保持恒定，D =30 mm，hw=60 mm，U =167 mm/s。采用粒子图像测速技术（PIV）测量了近尾流区的瞬时速度场和时均速度场。为了研究浸没的影响，将圆柱体放置在底部和自由表面之间的八个不同高度（hD）处（从7.5 mm到60 mm，以7.5 mm为增量）。采用瞬时速度矢量场、时均速度矢量场、相应的流线型和雷诺应力关联式分析了水平圆柱下游的流动特性。利用500幅瞬时图像得到了平均速度矢量场、相应的流线拓扑和雷诺应力关联式。在hD/D=0.25 ~ 1的范围内，随着浸没高度比（hD/D）的增大，射流速度增大。时均流动特性表明，旋转方向不同，初生循环气泡和发展循环气泡之间存在差异。这种情况的发生导致卷吸，这刺激的核心和尾流区之间的动量传递为hD/D=1和2的情况。
Flow characteristics around a horizontal circular cylinder were investigated in shallow water. The diameter of circular cylinder, the height of shallow water and free stream velocity were kept constant during the experiments asD=30 mm,hw=60 mm andU=167 mm/s, respectively. Particle Image Velocimetry (PIV) was used to measure instantaneous and time-averaged velocity vector fields in the near wake region. In order to investigate the effect of immersion, the cylinder was placed at eight different elevations (hD) between bottom and free surface (from 7.5 to 60 mm with 7.5 mm increments). Instantaneous and time-averaged velocity vector field, corresponding streamline patterns and Reynolds stress correlation were used to analyze the behavior of the flow downstream of horizontal cylinder. The mean velocity vector field, corresponding streamline topology and Reynolds stress correlation were obtained using 500 instantaneous images. As the immersion level ratio (hD/D) increases, the magnitude of jet-like flow velocity goes up ranged fromhD/D=0.25–1. Time averaged flow characteristics show that there is a difference between primary and developing circulation bubble depending on direction of rotation. This occurrence causes the entrainment and this stimulates the momentum transfer between the core and wake flow region forhD/D=1 and 2 cases.