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Unified Criterion for Clear‐Water Local Scour Induced by Junction Flows and Wall Jets
Author(s) -
Cheng NianSheng,
Lu Yesheng,
Wei Maoxing,
Chiew YeeMeng
Publication year - 2021
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2020wr028804
Subject(s) - froude number , hydraulics , hydraulic structure , geotechnical engineering , geology , bed load , sediment transport , flow (mathematics) , scale (ratio) , culvert , bedform , sediment , mechanics , engineering , geomorphology , physics , quantum mechanics , aerospace engineering
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.