Flow pattern in the scour hole around a cylinder
Flow pattern in the scour hole around a cylinder
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DOI：
10.1080/00221680309499989
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发表时间：
2003-07
影响因子：
2.3
通讯作者：
K. Babaeyan-Koopaei
中科院分区：
文献类型：
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作者：
K. Babaeyan-Koopaei
祝贺作者提出了一个有趣的文件，一个复杂的现象，绕圆形桥墩的流动模式。这个问题引起了许多研究人员的兴趣，并在过去几十年中一直在研究，例如汤森（1947）、Chabert和Engeldinger（1956）、Roshko（1961）、Belik（1973）、梅尔维尔和劳基维（1977）、Breusers等人（1977）、Baker（1978）。Ettema（1980），Raudkivi和Sutherland（1981），Dargahi（1987），小林等（1997），Babaeyan-Koopaei和Valentine（1999），Ting（2001），等等。流动显示是在一个16米长，0.3米宽，0.3米深的倾斜水槽。水槽床由dso = 6.5 mm的分级砾石沉积物组成。流中接种有中性浮力示踪剂，并由可移动托架中的卤素灯发出的0.5 m长× 5 mm宽的垂直光片照亮。示踪剂运动的记录是用数字视频或固定在车厢上的静态摄像机进行的（图1）。图2（a）中示出了使用该技术获得的图像的示例。它清楚地显示了桥墩前面的下降流，桥墩上游的强涡流，以及桥墩下游的抛落涡流和尾流涡流。它也证实了图2（B）中所示的Ahmed和Rajaratnam（1998）测量的速度矢量V的变化性质，即在不同的流动深度处，速度矢量的俯仰角在圆柱表面附近非常接近-90°。作者指出，在实验中，在圆柱体上游的冲刷坑中观察到一系列的四个旋涡，即边缘处的顺时针强旋涡，x ~-35cm处的弱逆时针旋涡，x ~-10cm处的相当强的顺时针旋涡，以及冲刷坑其余部分的顺时针旋涡。Baker（1978）。和Dargahi（1987），这些涡旋的位置随
The Authors are congratulated on presenting an interesting paper on a complex phenomenon concerning the flow pattern around circular bridge piers. This problem has been of interest to a large number of researchers and has been researched on for the past few decades e.g. Townsend (1947), Chabert and Engeldinger (1956), Roshko (1961), Belik (1973), Melville and Raudkivi (1977), Breusers et al (1977), Baker (1978). Ettema (1980), Raudkivi and Sutherland (1981), Dargahi (1987), Kobayashi et al. (1997), Babaeyan-Koopaei and Valentine (1999), Ting (2001), and the list still goes on. The Discusser has also carried out flow visualization of the flow pattern around circular piers. The flow visualization was conducted in a 16 m long, 0.3 m wide by 0.3 m deep tilting flume. The flume bed was composed of graded gravel sediments with dso = 6.5 mm. The flow was seeded with neutrally buoyant tracers and illuminated by a 0.5 m long by 5 mm wide vertical light sheet from a halogen lamp contained in a movable carriage. Recordings of the tracers' motion were made with a digital video or a still camera attached to the carriage (Fig. 1). An example of the image obtained with the use of this technique is shown in Fig. 2(a). It clearly shows the downflow in front of the pier, a strong vortex directly upstream of the pier, and the cast-off and wake vortices downstream of the pier. It does also confirm the nature of change in velocity vector V, measured by Ahmed and Rajaratnam (1998) shown in Fig. 2(b), that at different flow depths the pitch angle of the velocity vector is very close to —90° near the cylinder surface. The Authors have indicated that in their experiment they have observed a series of four vortices in the scour hole upstream of the cylinder i.e. a clockwise strong vortex at the brink, a weak counter-clockwise vortex at x ~ —35 cm, a rather strong clock wise vortex at x ~ —10 cm, and another clockwise vortex in the remaining part of the scour hole. According to Baker (1978). and Dargahi (1987) the positions of these vortices vary with the