Local scour in a sediment bed varies depending on the type, size and shape of hydraulic structures, and the properties of approach flow and sediment particles. Published studies are hitherto confined primarily to empirical experiments based on particular types of hydraulic structure and there is almost no comparison of scour amongst different types of hydraulic structures. This study aims to provide an attempt to unify different types of clear‐water scour based on a new length scale, which is proposed to characterize the size of the large‐scale flow structure that governs scouring processes. The new length scale serves as a generalized hydraulic radius, which is applicable for all types of clear‐water scour related to junction flows at bridge piers and abutments, and wall jets including culverts. The analysis indicates that when normalized with the new length scale, the equilibrium scour depths can be described with a unified function of the densimetric Froude number, regardless of different scour types. In addition, this study also shows that the proposed function varies with the scour efficiency, in a fashion resembling the bedload function in the range of low to high transport regimes. This finding, which is founded on solid physical grounds, reveals that different kinds of local scour phenomena can be interpreted in unison rather than based on the individual type of hydraulic structures.

中文翻译：

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交界处流动和壁面射流引起的清水局部冲刷统一标准

沉积床中的局部冲刷量取决于水工建筑物的类型，大小和形状以及进水流和沉积物颗粒的性质。迄今为止，已发表的研究主要限于基于特定类型的水工结构的经验实验，几乎没有比较不同类型水工结构之间冲刷的比较。这项研究的目的是尝试基于新的长度尺度来统一不同类型的清水冲刷，提出该尺度以表征控制冲刷过程的大型流动结构的大小。新的长度标尺用作通用的水力半径，适用于与桥墩和桥台的交界处流以及包括涵洞在内的墙面射流有关的所有类型的清水冲刷。分析表明，当使用新的长度标度进行归一化时，无论冲刷类型如何，都可以使用密度弗洛德数的统一函数描述平衡冲刷深度。此外，这项研究还表明，拟议的功能随冲刷效率的变化而变化，其方式类似于在低到高运输范围内的床载功能。基于坚实的物理基础的这一发现表明，可以统一地解释不同种类的局部冲刷现象，而不是根据水力结构的单个类型来解释。这项研究还表明，拟议的功能随冲刷效率的变化而变化，其方式类似于在低到高运输范围内的床载功能。基于坚实的物理基础的这一发现表明，可以统一地解释不同种类的局部冲刷现象，而不是根据水力结构的单个类型来解释。这项研究还表明，拟议的功能随冲刷效率的变化而变化，其方式类似于在低到高运输范围内的床载功能。基于坚实的物理基础的这一发现表明，可以统一地解释不同种类的局部冲刷现象，而不是根据水力结构的单个类型来解释。