Influence of compound bedforms on hydraulic roughness in a tidal environment
Influence of compound bedforms on hydraulic roughness in a tidal environment
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潮汐环境中复合地床形态对水力粗糙度的影响
DOI：
10.1007/s10236-011-0476-6
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发表时间：
2011
期刊：
影响因子：
2.3
通讯作者：
Winter
中科院分区：
文献类型：
--
作者：
Lefebvre;Ernstsen;Winter
海底形态对水流的影响通常用水力粗糙度来表示，水力粗糙度是理解和模拟沿海地区水文和沉积物动力学的基本参数。这项研究量化了整个潮汐周期中大型复合床型的水力粗糙度，并研究了其与平均床型尺寸的关系。使用声学多普勒电流剖面仪和多波束回声测深仪在 Jade 潮汐通道（德国北海）中沿着大型复合床型进行了连续测量，该复合床型包括面向落潮的主要床型和叠加的较小次生床型。空间平均速度分布产生对数线性关系，用于计算粗糙度长度。在洪水阶段，速度剖面最好通过与次生地床形状产生的粗糙度相关的单个对数线性拟合来描述。在落潮阶段，速度剖面被分段，显示至少存在两个边界层：下部边界层与叠加的次生河床形态成比例，上部边界层与面向落潮的主要河床形态成比例。建议在落潮阶段由主要床型引起的阻力与床型下游侧的流动膨胀、分离和再循环有关。测试了三个现有公式，以根据局部床形尺寸预测粗糙度长度。这三个人都预测了平均粗糙度长度的正确数量级，但未能预测其在潮汐周期中的变化。
The effect exerted by the seabed morphology on the flow is commonly expressed by the hydraulic roughness, a fundamental parameter in the understanding and simulation of hydro- and sediment dynamics in coastal areas. This study quantifies the hydraulic roughness of large compound bedforms throughout a tidal cycle and investigates its relationship to averaged bedform dimensions. Consecutive measurements with an acoustic Doppler current profiler and a multibeam echosounder were carried out in the Jade tidal channel (North Sea, Germany) along large compound bedforms comprising ebb-oriented primary bedforms with superimposed smaller secondary bedforms. Spatially averaged velocity profiles produced log-linear relationships which were used to calculate roughness lengths. During the flood phase, the velocity profiles were best described by a single log-linear fit related to the roughness created by the secondary bedforms. During the ebb phase, the velocity profiles were segmented, showing the existence of at least two boundary layers: a lower one scaling with the superimposed secondary bedforms and an upper one scaling with the ebb-oriented primary bedforms. The drag induced by the primary bedform during the ebb phase is suggested to be related to flow expansion, separation, and recirculation on the downstream side of the bedform. Three existing formulas were tested to predict roughness lengths from the local bedform dimensions. All three predicted the right order of magnitude for the average roughness length but failed to predict its variation over the tidal cycle.
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DOI：
--
发表时间：
2010
期刊：
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1976
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作者：
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D. Swart
影响因子：
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作者：
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DOI：
--
发表时间：
2009
期刊：
影响因子：
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作者：
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通讯作者：
D. Hebbeln