Local scour around submerged bell mouth groin for different orientations
01 Jan 2011-
TL;DR: In this article, an experimental study was performed in a 45.6m long and 2.45m wide laboratory water basin to investigate the local scour around a bellmouth groin structure.
Abstract: Groins are the most popular techniques for riverbank stabilization that are constructed along the channel bank to locally change river conditions, thereby creating a flow condition that promotes navigability and diverts the flow away from the bank. An experimental study was undertaken in a 45.6m long and 2.45m wide laboratory water basin to investigate the local scour around a bellmouth groin structure. A total number of 12 test runs were performed for different flow conditions. Three different discharges and four different angles with submerged groin condition were considered in the present study. Therefore, twelve tests were conducted with submerged condition of which six had a water depth of 22 cm and the rest six had a flow depth of 26 cm. All tests were conducted for 8 hours duration in clear water condition. In order to avoid the ripple formation, the coarse sand with d50 = 0.75 mm was selected as bed material. Scour depth for 90 angled groins was observed to be the maximum and for 135 it was the minimum. The time to reach maximum scour depth was found to vary with discharge and angle of attack. The study also revealed that maximum scour depth and deposition pattern is changed with changing the condition of flow and groin orientations. Scour depth varied with velocity variation of flow, and an increasing tendency of scour depth has been observed with increasing flow intensity. Maximum scour depth shows an increasing trend with increasing Froude number.
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TL;DR: In this paper, the influence of cohesion on scour depth around submerged spur dike founded in the mixtures of cohesive sediment consisting of clay-gravel and clay-sandgravel.
Abstract: This study presents the influence of cohesion on scour depth around submerged spur dike founded in the mixtures of cohesive sediment consisting of clay–gravel and clay–sand–gravel. Studies related to scour around submerged dike founded in such type of cohesive sediment mixtures are not reported in the literature to best of our knowledge. All experiments were conducted with singular submerged spur dike under clear water flow conditions. The process of scour around submerged spur dike founded in clay–gravel/clay–sand–gravel mixtures was found significantly different from that of cohesionless sediments. The process, geometry and scour depth around submerged spur dike in cohesive sediments were significantly affected by clay percentage and unconfined compressive strength of cohesive sediment mixtures. Relationships are proposed for the assessment of scour depth at nose and, at the wake of submerged spur dike in cohesive sediments mixtures. The proposed relationships give satisfactory agreement between observe...
12 citations
TL;DR: In this article, a comparison of the published experimental data on scour depths at bridge piers shows a large range of values at what appears to be identical conditions, and it was decided to investigate whether or not this variation could arise from different grain-size distributions of the bed material used.
Abstract: A comparison of the published experimental data on scour depths at bridge piers shows a large range of values at what appears to be identical conditions. It was therefore decided to investigate whether or not this variation could arise from different grain-size distributions of the bed material used. The experiments were carried out in a reecirculating flume 38 m long, 1.5 m wide, and 1.2 m deep, using a 100 mm-diam cylindrical pier. In the experiments, the \\id\\d5\\d0 grain size and the grain-size distribution were systematically varied. Trial runs showed that for a given shear velocity, depth of flow greater than about two pier diameters had no observable effect on the depth of scour, and thereafter all tests were run at a flow depth of 0.60m, or six pier diameters. The velocity of the approach flow and the shear velocities were determined from the slope of the velocity distribution. Details of the study have been reported by Ettema together with a detailed evaluation of the development of the scour hole.
2 citations
Dissertation•
01 Aug 1983
2 citations
References
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TL;DR: In this paper, an integrated approach to the estimation of local scour depth at bridge piers and abutments, collectively termed bridge foundations, is presented, based on empirical relations, termed K-factors, that account for the effects on scour depths of flow depth and foundation size, flow intensity, sediment characteristics, foundation type, shape and alignment, and approach channel geometry.
Abstract: This paper summarizes many of the results from an extensive program of bridge scour research undertaken at The University of Auckland, New Zealand. An integrated approach to the estimation of local scour depth at bridge piers and abutments, collectively termed bridge foundations, is presented. The design method is based on empirical relations, termed K-factors, that account for the effects on scour depth of flow depth and foundation size, flow intensity, sediment characteristics, foundation type, shape and alignment, and approach channel geometry. The K-factors are evaluated by fitting envelope curves to existing data for piers and abutments and a new extensive data set for abutments. The new data are discussed and presented. Application of the design method is illustrated in examples.
567 citations
Book•
08 Feb 1988
TL;DR: The authors collects and collates the significant advances in analytical methods for alluvial channel design, river morphology, and mathematical simulation of river channel changes from an engineering point of view, and presents a complete analytical treatment of river morphology and its responses to environmental and human-made changes from the engineering perspective.
Abstract: This text collects and collates the significant advances in analytical methods for alluvial channel design, river morphology, and mathematical simulation of river channel changes. It presents a complete analytical treatment of river morphology and its responses to environmental and human-made changes from the engineering point of view. For professionals in flood control, bridge design, irrigation and waterways, this book is a current, comprehensive refresher and reference. It is also a textbook in river sedimentation. Analytical and empirical methods are detailed for solving erosion and sedimentation problems, hydraulic design of channels, bridges, and related structures. From a sound physical foundation, mathematical techniques are presented for simulating river channel changes, and computer-aided analysis and design for river projects are illustrated by abundant examples.
475 citations
"Local scour around submerged bell m..." refers background in this paper
...From the engineering point of view, one is always interested in determining the potential scour so that the provision can be made in design and construction (Chang, 1988)....
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TL;DR: In this paper, the authors analyzed the effects of abutment length, flow depth, and shape and alignment on local scour depth at bridge abutments, and showed that the maximum scour depths measured in the laboratory for these cases are 2L and 10 y.
Abstract: Laboratory data for local scour depth at bridge abutments are presented. These include sufficient data to demonstrate the effects on scour depth of abutment length, flow depth, and abutment shape and alignment. In addition, some data for the effects of sediment characteristics, flow intensity, and approach channel geometry are given. The data are rationalized in terms of the ratio of abutment length to flow depth, L/y. Two limiting cases are identified. For large and small values of L/y, the abutments are termed long and short, respectively, and it is shown that the maximum scour depths measured in the laboratory for these cases are 2L and 10 y. Most actual cases of abutment scour lie between the limiting cases, and it is demonstrated that, in such situations, scour depth is proportional to the square root of the product L/y. These relationships are formulated in a simple design method, which is used on some illustrative examples. Limitations to the design method are discussed.
348 citations
"Local scour around submerged bell m..." refers background in this paper
...Recent studies have included Rajaratnam and Nwachukwu (1983), Melville (1992)....
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TL;DR: In this paper, the authors present the results of an experimental study on the structure of turbulent flow near groin-like structures, where the deflected flow has been analyzed using the model of the three-dimensional turbulent boundary layer.
Abstract: This paper presents the results of an experimental study on the structure of turbulent flow near groin‐like structures. Based on experimental observations, the deflected flow has been analyzed using the model of the three‐dimensional turbulent boundary layer. The flow bounded by the separating stream line, the groin, and the adjacent bank has been analyzed by treating it as a shear layer in which the velocity profiles have been found to be similar. The amplified bed shear stress near the groin has also been analyzed using the similarity idea. Even though the majority of the present experiments were done with the thin‐plate groin, some observations were also made on a groin with a semicylindrical hose.
210 citations
TL;DR: In this article, it is shown that a simple kinematic model for erosion of sand beds in a long contraction, first proposed by Straub, can be modified for application to erosion around spur dikes.
Abstract: The present status of research on erosion of sand beds around spur dikes is briefly reviewed. The experimental results of erosion of two different sizes of nearly uniform sand are presented. It is shown that a rather simple kinematic model for erosion of sand beds in a long contraction, first proposed by Straub, can be modified for application to erosion around spur dikes. The equilibrium depth of scour depends on the size of the sand and the flow depth upstream of the location of the spur dike. This is consistent with Laursen's observations around bridge piers.
185 citations