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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Examining the physical components of boundary shear stress for water-worked gravel deposits
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Examining the physical components of boundary shear stress for water-worked gravel deposits

机译：检查水工砾石矿床边界切应力的物理组成

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It is argued in this commentary that, in order to understand better the physical mechanisms that generate boundary shear stress over water-worked gravel beds, flow velocity data should be re-evaluated by spatial averaging the Reynolds equations to produce time- and space-averaged (double-averaged) momentum equations. A series of laboratory experiments were conducted in which the flow velocities were measured using a PIV system over two water-worked gravel deposits. Combined with detailed data on the bed surface topography and vertical porosity, the physical components of shear stress were obtained. This enabled the various momentum transfer mechanisms present above, within and at the interface of a porous, fluvial deposit, to be quantified. This included the examination of the relevant contributions of temporal and spatial fluctuations in velocity and surface drag to the overall momentum transfer. It is demonstrated that double-averaging represents a logical framework for assessing the fluid forces responsible for sediment entrainment and for investigating intragravel flow and sediment-water interface exchange mechanisms within the roughness layer in water-worked gravel deposits. By considering the physical components of shear stress and their relative sizes it was possible to provide a physically based explanation for existing observations of enhanced mobility of gravel-sand mixtures and the transfer of solutes into porous, gravel deposits. This analysis reveals the importance of obtaining co-located, high quality spatial data on the flow field and bed surface topography in order to gain a physical understanding of the mechanisms which generate boundary shear stress.
机译：该评论认为，为了更好地理解在水处理砾石床上产生边界剪切应力的物理机制，应通过对雷诺方程进行空间平均以产生时间和空间平均来重新评估流速数据。 （双平均）动量方程。进行了一系列的实验室实验，其中使用PIV系统在两个水处理的砾石沉积物上测量了流速。结合床面形貌和垂直孔隙率的详细数据，获得了切应力的物理分量。这使得上面，多孔的，河流沉积物内部和界面处存在的各种动量传递机制得以量化。这包括检查速度和表面阻力的时空波动对整体动量传递的相关贡献。结果表明，两次平均代表了一个逻辑框架，用于评估造成泥沙夹带的流体力，并研究在水处理砾石矿床的粗糙层内的砾石内部流动和沉积物-水界面交换机制。通过考虑剪切应力的物理成分及其相对大小，可以为现有的砾石-砂混合物流动性增强和溶质向多孔砾石沉积物转移的观测结果提供基于物理的解释。该分析揭示了获得关于流场和床表面地形的同位高质量空间数据的重要性，以便对产生边界剪切应力的机理有一个物理的了解。

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