Three-dimensional flow structure and bed morphology in large elongate meander loops with different outer bank roughness characteristics
Three-dimensional flow structure and bed morphology in large elongate meander loops with different outer bank roughness characteristics
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DOI：
10.1002/2016wr019040
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发表时间：
2016-12-01
影响因子：
5.4
通讯作者：
Garcia, Marcelo H.
中科院分区：
文献类型：
--
作者：
Konsoer, Kory M.;Rhoads, Bruce L.;Garcia, Marcelo H.
很少有研究探讨了三维流动结构和床形态内的细长环路的大型蜿蜒的渠道。本研究的重点是三维流动结构和床形态的空间格局在两个细长的曲流环路，并探讨如何在外银行粗糙度的差异影响近银行的流动特性。在两个不同的事件-近岸流和漫滩事件的三维速度进行了测量。在一次近平岸事件中获得了关于航道水深和河床形态几何形状的详细数据。环路内的水流结构的特征是：点坝强烈的地形转向，与水流曲率相关的螺旋运动的发展，以及基岩沿着外侧河岸暴露的水流加速。漫滩事件期间的近岸流速小于近岸流的流速，突出了点坝对次岸流阶段水流质量和动量再分布的强烈影响。多个外滩池是明显的细长弯曲环路内具有较低的外银行粗糙度，但不存在于环路外银行粗糙度高，这可能反映了丰富的大型木质残体对近岸流速特征的影响。两个环路内水池的位置可以与平面曲率的空间变化相联系。研究结果表明，在这些大的细长环的流动结构和床的形态是类似的，在小的细长环，但有些不同的流动结构和床的形态报告的实验细长环。
Few studies have examined the three-dimensional flow structure and bed morphology within elongate loops of large meandering channels. The present study focuses on the spatial patterns of three-dimensional flow structure and bed morphology within two elongate meander loops and examines how differences in outer bank roughness influence near-bank flow characteristics. Three-dimensional velocities were measured during two different events-a near-bankfull flow and an overbank event. Detailed data on channel bathymetry and bed form geometry were obtained during a near-bankfull event. Flow structure within the loops is characterized by strong topographic steering by the point bar, by the development of helical motion associated with flow curvature, and by acceleration of flow where bedrock is exposed along the outer bank. Near-bank velocities during the overbank event are less than those for the near-bankfull flow, highlighting the strong influence of the point bar on redistribution of mass and momentum of the flow at subbankfull stages. Multiple outer bank pools are evident within the elongate meander loop with low outer bank roughness, but are not present in the loop with high outer bank roughness, which may reflect the influence of abundant large woody debris on near-bank velocity characteristics. The positions of pools within both loops can be linked to spatial variations in planform curvature. The findings indicate that flow structure and bed morphology in these large elongate loops is similar to that in small elongate loops, but differs somewhat from flow structure and bed morphology reported for experimental elongate loops.