An experimental study of the incipient bed shear stress partition in mobile bed channels filled with emergent rigid vegetation

Wang, Hao; Tang, Hongwu; Yuan, Saiyu; Lv, Sheng-qi; Zhao, Xuanyu

doi:10.1007/s11431-014-5549-6

Cited by 29 publications

(13 citation statements)

References 15 publications

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“…Wang et al (2014) showed that when the sediment was in the stage of incipient motion, the bed shear stress could be divided into two parts: the grain shear stress and the shear stress caused by sand dunes, which are the bed form after it has been deformed by the sediment incipient motion. The criterion for the sediment incipient motion adopted in Tang et al (2013) and Wang et al (2014) is similar to that without vegetation proposed by Kramer (Zhang 1998), i.e., the moment when there are few countable sediment particles on the bed beginning to move. Both of them are qualitative but can express the stage of the incipient motion of sediment very well.…”

Section: Introductionmentioning

confidence: 99%

Incipient motion of sediment in presence of submerged flexible vegetation

Wang

Tang

Zhao

et al. 2015

Water Science and Engineering

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y., Lü, S.-q., Incipient motion of sediment in presence of submerged flexible vegetation, Water Science and Engineering (2015), Abstract:The presence of submerged vegetation on river beds can change the water flow structure and alter the state of sediment motion. In this study, the incipient motion of sediment in the presence of submerged flexible vegetation in open channels was investigated in a laboratory experiment. The vegetation was simulated with flexible rubber cylinders arranged in parallel arrays. The effect of the vegetation density, water depth, and sediment grain size on the incipient motion was investigated. The experimental results indicate that the incipient motion velocity of sediment increases as the vegetation density decreases and the water depth and sediment grain size increase. With flexible plants, the incipient motion velocity of sediment is lower than it is without vegetation, and is larger than it is with rigid vegetation. A general incipient motion velocity equation was derived, which can be applied to both flexible and rigid vegetation conditions.

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Section: Introductionmentioning

confidence: 99%

Incipient motion of sediment in presence of submerged flexible vegetation

Wang

Tang

Zhao

et al. 2015

Water Science and Engineering

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“…Firstly, the dimensionless drag force, also called drag force coefficient C D , is higher for an isolated square cylinder than for an isolated circular cylinder: for 10 4 ≤ R l ≤ 10 6 , C D = 2.1 for a square cylinder, while C D = 1.2 for a circular cylinder (Hoerner, 1965). Secondly, the variation in C D with planar density λ is converse for arrays of square and circular cylinders: C D increases with λ for square cylinders and 0 ≤ λ ≤ 0.25 (Buccolieri, Wigö, Sandberg, & Di Sabatino, 2016;Leonardi & Castro, 2010;Ludeña, Lopez, Rivière, & Mignot, 2017, August), while C D decreases for circular cylinders with λ, for 0.0047 ≤ λ ≤ 0.12 (Liu & Zeng, 2017;H. Wang, Tang, Yuan, Lv, & Zhao, 2014).…”

Section: Square Versus Circular Cylindersmentioning

confidence: 97%

Transverse surface waves in steady uniform and non-uniform flows through an array of emergent and slightly submerged square cylinders

Chetibi

Proust²,

Benmamar

2019

Journal of Hydraulic Research

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Steady uniform and non-uniform flows through an array of emergent and slightly submerged square cylinders are experimentally investigated with a specific focus on transverse seiche waves induced by vortex shedding. The study is first and foremost aimed at assessing the effect of streamwise flow non-uniformity on seiche waves. Its secondary purpose is to investigate the change in seiche magnitude, when initially emerged cylinders become slightly submerged. Thirdly and lastly, the effect of seiche waves on mean velocities and velocity fluctuations is quantified. The lock-in process between waves and vortex shedding is unaltered by flow non-uniformity and by a change from cylinder emergence to submergence. For non-uniform flows, this results in the coexistence of two differently oscillating transverse waves close to each other. Relative wave amplitude is found to be mainly influenced by relative submergence in the case of submerged cylinders, and by Froude number and oscillation mode in the case of emergent cylinders. Finally, seiche waves modify the streamwise mean velocity, when cylinders are emergent.

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“…Using experimental data from several authors (random, staggered, only two cases linear), suitably unified, they showed that the drag coefficient decreases monotonically with the increase in the vegetation Reynolds number and propose the two equations reported in Table 1, respectively, function of Re v and r v* with r v* dimensionless vegetation-related hydraulic radius. Wang et al [68], in a study for incipient bed shear stress partition in mobile bed channels, investigated the vegetation drag coefficient. By ignoring the bed surface shear stress, an empirical formula was developed by data fitting in which the drag coefficient is a function of the Reynolds number, calculated with the vegetation-related hydraulic radius of Cheng and Nguyen [67], the ratio between vegetation diameter and flow depth (D/h), and the vegetation density λ.…”

Section: Emergent Rigid Vegetationmentioning

confidence: 99%

“…Wang et al [68], in a study for incipient bed shear stress partition in mobile bed channels, investigated the vegetation drag coefficient. By ignoring the bed surface shear stress, an empirical formula was developed by data fitting in which the drag coefficient is a function of the Reynolds number, calculated with the vegetation-related hydraulic radius of Cheng and Nguyen [67], the ratio between vegetation diameter and flow depth (D/h), and the vegetation density .…”

Section: Emergent Rigid Vegetationmentioning

confidence: 99%

Flow Resistance in Open Channel Due to Vegetation at Reach Scale: A Review

D’Ippolito

Calomino

Alfonsi

et al. 2021

Water

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Vegetation on the banks and flooding areas of watercourses significantly affects energy losses. To take the latter into account, computational models make use of resistance coefficients based on the evaluation of bed and walls roughness besides the resistance to flow offered by vegetation. This paper, after summarizing the classical approaches based on descriptions and pictures, considers the recent advancements related to the analytical methods relative both to rigid and flexible vegetation. In particular, emergent rigid vegetation is first analyzed by focusing on the methods for determining the drag coefficient, then submerged rigid vegetation is analyzed, highlighting briefly the principles on which the different models are based and recalling the comparisons made in the literature. Then, the models used in the case of both emergent and submerged rigid vegetation are highlighted. As to flexible vegetation, the paper reminds first the flow conditions that cause the vegetation to lay on the channel bed, and then the classical resistance laws that were developed for the design of irrigation canals. The most recent developments in the case of submerged and emergent flexible vegetation are then presented. Since turbulence studies should be considered as the basis of flow resistance, even though the path toward practical use is still long, the new developments in the field of 3D numerical methods are briefly reviewed, presently used to assess the characteristics of turbulence and the transport of sediments and pollutants. The use of remote sensing to map riparian vegetation and estimating biomechanical parameters is briefly analyzed. Finally, some applications are presented, aimed at highlighting, in real cases, the influence exerted by vegetation on water depth and maintenance interventions.

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An experimental study of the incipient bed shear stress partition in mobile bed channels filled with emergent rigid vegetation

Cited by 29 publications

References 15 publications

Incipient motion of sediment in presence of submerged flexible vegetation

Incipient motion of sediment in presence of submerged flexible vegetation

Transverse surface waves in steady uniform and non-uniform flows through an array of emergent and slightly submerged square cylinders

Flow Resistance in Open Channel Due to Vegetation at Reach Scale: A Review

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