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首页> 外文期刊>Water resources research >Estimating bed shear stress from remotely measured surface turbulent dissipation fields in open channel flows
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Estimating bed shear stress from remotely measured surface turbulent dissipation fields in open channel flows

机译：从明渠水流中的遥测表面湍流耗散场估算床层切应力

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摘要

Synoptic information on bed shear stress is necessary in predicting the transport of sediments and environmental contaminants in rivers and open channels. Existing methods of estimating bed shear stress typically involve measuring vertical profiles of streamwise velocity or Reynolds stress and taking advantage of the logarithmic or the constant stress region, respectively, to determine friction velocity and subsequently, bed shear stress. While effective, these methods yield local measurements of bed shear stress only. Direct measurements of bed shear stress can also be obtained through measurements with a drag plate. However, this method yields average shear stress information over the area of the plate and is impractical for large-scale implementation in the field. Here we present a method capable of providing continuous synoptic measurements of bed shear stress over a large field-of-view. A series of Large-Scale Particle Image Velocimetry (LSPIV) and Acoustic Doppler Velocimetry (ADV) measurements were made in a variety of flows generated in a wide-open channel facility. Turbulent dissipation is calculated on the free surface from the 2-D LSPIV results and is correlated with near-surface ADV measurements of turbulent dissipation in the water column. The ADV results are consistent with the Nezu (1977) established relationship for the vertical variation of turbulent dissipation in the water column. Knowledge of the correlation between free-surface and near-surface dissipation values coupled with Nezu's (1977) relationship allow a robust and accurate estimate of friction velocity to be made and subsequently, shear stress at the bed can be estimated.
机译：有关河床切应力的天气信息对于预测河流和明渠中的沉积物和环境污染物的运输非常必要。估计床层剪切应力的现有方法通常包括测量水流速度或雷诺应力的垂直剖面，并分别利用对数或恒定应力区域来确定摩擦速度，然后确定床层剪切应力。虽然有效，但是这些方法仅能局部测量床层的剪切应力。床剪切应力的直接测量也可以通过用拖板进行测量来获得。但是，这种方法会产生整个平板区域的平均剪切应力信息，对于在现场进行大规模实施是不切实际的。在这里，我们提出了一种能够在大视野范围内提供连续的天气切变应力天气测量方法。在全开式通道设施中产生的各种流量中，进行了一系列大规模粒子图像测速（LSPIV）和声多普勒测速（ADV）测量。根据2-D LSPIV结果在自由表面上计算湍流耗散，并将其与水柱中湍流耗散的近表面ADV测量相关。 ADV结果与Nezu（1977）建立的水柱中湍流消散的垂直变化关系是一致的。认识到自由表面和近表面耗散值之间的相关性，再加上Nezu（1977）的关系，可以对摩擦速度进行可靠而准确的估算，随后可以估算床层的切应力。

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