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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Structure of flow over alluvial bedforms: an experiment on linking field and laboratory methods
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Structure of flow over alluvial bedforms: an experiment on linking field and laboratory methods

机译：冲积层流的流动结构：野外实验与实验室方法的联系

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This paper presents results of a field study designed to examine the structure of flow over mobile and fixed bedforms in a natural stream and to compare the results with findings of previous laboratory studies within the framework of double time-space averaging approach. Measurements of turbulence were obtained in a small river in Illinois, USA, over a fine spatial grid of sampling points above a mobile sandy bedform and its artificially moulded replica. Flow structure over the artificial bedform is similar to that observed in laboratory studies, but is markedly different from the flow structure over natural bedforms. These differences are most pronounced in the roughness sublayer, whereas How in the logarithmic layer over natural and artificial sand waves is fairly similar and exhibits spatial uniformity. The double time-space averaged distributions of turbulence statistics conform to the multilayer model of flow structure over bedforms. Mean velocity distributions indicate neither classical flow recirculation nor substantial reduction of velocities in the lee of bedform crests. However, vertical patterns of turbulence statistics over depth suggest that stacked wakes similar to those observed in laboratory studies exist above the bedforms. Thus, despite the absence of flow separation, wake development seems to be induced by the systematic influence of upstream bedforms on the vertical structure of turbulence. Copyright (c) 2006 John Wiley & Sons, Ltd.
机译：本文介绍了一项现场研究的结果，该研究旨在检查自然流中流动床和固定床的流动结构，并将结果与​​以前的实验室研究结果在双时空平均方法的框架内进行比较。湍流的测量是在美国伊利诺伊州的一条小河中，在移动的沙质岩床及其人工模制的复制品上方的采样点的精细空间网格上进行的。人造床形上的流动结构与实验室研究中观察到的相似，但与天然床形上的流动结构明显不同。这些差异在粗糙度子层中最为明显，而在自然和人工砂波上的对数层中How却非常相似，并且表现出空间均匀性。湍流统计量的双时空平均分布符合床体上流动结构的多层模型。平均速度分布既不表示经典的气流再循环，也不表示床形波峰背风的速度大幅降低。但是，深度上湍流统计的垂直模式表明，与床尾上方类似的叠层尾流类似于实验室研究中观察到的尾流。因此，尽管没有流动分离，但上游床形对湍流垂直结构的系统影响似乎诱发了尾流的发展。版权所有（c）2006 John Wiley＆Sons，Ltd.

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