Effects of vegetation patch density on flow velocity characteristics in an open channel

Li, Wenqi; Wang, Dan; Jiao, Jun-li; Yang, Kejun

doi:10.1007/s42241-018-0086-6

Cited by 36 publications

(19 citation statements)

References 21 publications

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“…However, in rivers and shallow lakes, aquatic plants often exist in patches with limited size and appear to be approximately circular [83][84] . Compared with the flow in fully vegetated channels, the flow through and around limited vegetation patches is more complicated [85][86][87][88][89][90][91] and has been the subject of detailed experiments recently [89] . As the incoming flow approaches the vegetation patch, the flow deflects laterally to both sides, and more importantly, a portion of the incoming flow passes through the vegetation patch, known as "bleeding flow".…”

Section: Flow Through and Around Finite Vegetation Patchesmentioning

confidence: 99%

Flow dynamics and sediment transport in vegetated rivers: A review

et al. 2021

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The significance of riparian vegetation on river flow and material transport is not in dispute. Conveyance laws, sediment erosion and deposition, and element cycling must all be adjusted from their canonical rough-wall boundary layer to accommodate the presence of aquatic plants. In turn, the growth and colonization of riparian vegetation are affected by fluvial processes and river morphology on longer time scales. These interactions and feedbacks at multiple time scales are now drawing significant attention within the research community given their relevance to river restoration. For this reason, a review summarizing methods, general laws, qualitative cognition, and quantitative models regarding the interplay between aquatic plants, flow dynamics, and sediment transport in vegetated rivers is in order. Shortcomings, pitfalls, knowledge gaps, and daunting challenges to the current state of knowledge are also covered. As a multidisciplinary research topic, a future research agenda and opportunities pertinent to river management and enhancement of ecosystem services are also highlighted.

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Section: Flow Through and Around Finite Vegetation Patchesmentioning

confidence: 99%

Flow dynamics and sediment transport in vegetated rivers: A review

et al. 2021

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“…In the past, the influence of the limited length of vegetation (Dan et al, 1996) and single circular patch (Anjum et al, 2018a;Chen et al, 2012;Li et al, 2019;Nishino et al, 2007;Tanaka et al, 1993) on the flow gained much attention. As there are very minute chances of the existence of individual patch on the floodplains and waterways, these patches usually exist in the series or scattered pattern with no uniform stem densities.…”

Section: Introductionmentioning

confidence: 99%

3D numerical modeling of flow characteristics in an open channel having in-line circular vegetation patches with varying density under submerged and emergent flow conditions

Tariq

Ghani

Anjum

et al. 2022

Journal of Hydrology and Hydromechanics

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In the marine ecological system, the prime role of water management and durability of an ecosystem is being played by the vegetation patches. The vegetation patches in open channels can significantly affect the flow velocity, discharge capacity and hinder energy fluxes, which ultimately helps in controlling catastrophic floods. In this study, the numerical simulation for turbulent flow properties, i.e. velocity distribution, Reynolds stresses and Turbulent Intensities (TI) near the circular vegetation patches with progressively increasing density, were performed using the computational fluid dynamics (CFD) code ANSYS FLUENT. For examination of the turbulent flow features in the presence of circular patches with variable densities, Reynolds averaged Navier-Stokes equations, and Reynolds stress model (RSM) were employed. The numerical investigation was performed in the presence of in-line emergent and submerged patches having variable vegetation density in the downstream direction. Two of the cases were investigated with three circular patches having a clear gap to patch diameter ratio of La/D = 1 (where La is the clear spacing between the vegetation patches and D is the diameter of the circular patch), and the other two cases were analyzed with two patches having a clear gap ratio of La/D = 3. The case with a clear gap ratio (La/D = 3) showed 10.6% and 153% inflation in the magnitude of longitudinal velocity at the downstream of the sparse patch (aD = 0.8) and upstream of the dense patch (aD = 3.54), respectively (where aD is the flow blockage, in which “a” represents the patch frontal area and “D” represents the patch diameter). The velocity was reduced to 94% for emergent and 99% for submerged vegetation due to successive increase in vegetation density made by introducing a middle patch which reduced the clear gap ratio (La/D = 1). For La/D = 1, the longitudinal velocities at depth z = 15cm were increased by 319% than at depth z = 6cm at the downstream of the dense patch (aD = 3.54). Whereas it was observed to 365% higher in the case of La/D = 3. The magnitude of turbulent characteristics was observed 36% higher for submerged vegetation cases having a clear gap ratio of La/D = 1. The successive increase in the patch density reduced the Reynolds stresses, turbulent kinetic energy and turbulent intensities significantly within the gap region. The major reduction in the flow velocities and turbulent properties in the gaps provides a stable environment for aquatic ecosystems nourishment and fosters sediment deposition, and supports further vegetation growth.

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“…While the evaluation of flow resistance with reference to river reach is of considerable importance, it must be said that even the effect of vegetation patches exert considerable influence on flow resistance, on velocity distribution, and solid transport, and this is also a field of further research as witnessed by recent publications [34][35][36][37][38]. The kinetics of vegetation in terms of establishment, growth, and decay of riparian vegetation in response to dynamic hydraulic conditions are also beginning to be of interest to researchers [45,142].…”

Section: Future Research and Conclusionmentioning

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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Effects of vegetation patch density on flow velocity characteristics in an open channel

Cited by 36 publications

References 21 publications

Flow dynamics and sediment transport in vegetated rivers: A review

Flow dynamics and sediment transport in vegetated rivers: A review

3D numerical modeling of flow characteristics in an open channel having in-line circular vegetation patches with varying density under submerged and emergent flow conditions

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

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