Assessment of a River Reach for Environmental Fluid Dynamics Studies
Assessment of a River Reach for Environmental Fluid Dynamics Studies
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DOI：
10.1061/(asce)hy.1943-7900.0000267
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发表时间：
2010-04
影响因子：
2.4
通讯作者：
A. Sukhodolov;W. Uijttewaal
中科院分区：
文献类型：
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作者：
A. Sukhodolov;W. Uijttewaal
湍流是控制河流流动中能量传递的基本机制，通常在实验室水槽中进行研究。最近，人们观察到一种趋势，即建造更大规模的室外设施，以避免实验结果放大的问题。本文介绍了在用作环境野外实验室的河道上进行的实验研究的结果。研究的重点是了解流动结构的空间分布及其对流动时间变异性的依赖。利用多普勒测速仪进行了详细的测量，并应用明渠流动理论对其进行了分析。结果表明，河段的水流结构类似于典型的三维明渠水流特征。在远离河岸的地方，水流表现为准二维完全发育的湍流明渠流，从而为浅层混合层和淹没水生植物斑块流动的现场实验研究提供了有利条件。在湍流剪切应力模式的季节动力学中，一个有趣的观察结果是，流的中心部分粗糙度层的高度降低，尽管总体粗糙度系数增加。与此同时，河岸附近的二次流结构也发生了很大的变化，低水位观测到的二次循环被中水位观测到的流动分离和内边界层所取代。
Turbulence is the fundamental mechanism governing energy transfer in river flows that was conventionally examined in laboratory flumes. Recently, a trend has been observed for constructing larger scale and outdoor facilities that tend to avoid the problems of upscaling of experimental results. This paper presents the results of an experimental study performed on a river reach used as an environmental field laboratory. The study is focused on the understanding of the spatial arrangement of the flow structure and its dependency on the temporal variability of the flow. Detailed measurements were taken using acoustic Doppler velocimeters and their analysis was completed applying the theory of open-channel flows. The obtained results reveal that the flow structure on the river reach resembles characteristics of a typical three-dimensional open-channel flow. Away from the riverbanks, the flow behaves as a quasi-two-dimensional fully developed turbulent open-channel flow thus providing conditions favorable for field experimental studies of shallow mixing layers and flows over patches of submerged aquatic plants. An interesting observation in the seasonal dynamics of turbulent shear stress patterns was that the height of the roughness layer was reduced in the central part of the flow, though the overall roughness coefficient was increased. At the same time, the structure of the secondary flow near the banks was also substantially altered as the secondary circulations observed at low water levels were replaced by flow separation and internal boundary layers at medium water levels.