丁坝群近体流动结构的可视化实验研究

摘要

The dye injection and oil-film method together with electromagnetic velocimeter are applied to measure the flow field around spur dikes.The observed information shows that the flow is three dimensional and unsteady due to the fluctuating circulation zone and surface wave.The dye injection clearly visualizes the flow pattern of instantaneous 3-D flow while the photos of oil film well demonstrate the scale and location of the eddies.The flow characteristics that obtained by using flow visualization technology are highly consistent with the velocity distribution measured by electromagnetic velocimeter.%本文介绍了用颜料示踪和最新的油膜技术对流动进行可视化记录以研究淹没丁坝群的近体流场分布的试验结果。结果表明绕丁坝的近场流动具有强三维非恒定特性，表现在坝后振荡回流区的形成和坝顶表面波的生成。在坝头的分离区，流动加速并伴有二次回流，形成该处冲刷的水力学条件。在深淹没条件下丁坝后面主回流区的形成主要受制于坝顶的绕流，以垂向方向的回流为主，同时也受到坝头侧面分离流的影响，产生水平方向的倾斜和扭转。颜料示踪捕捉到丁坝近体的瞬间三维流动形态，油膜照片则清晰地显示出了床底及侧壁的旋涡大小及位置。