Influence of Vegetation on Turbulence Characteristics and Reynolds Shear Stress in Partly Vegetated Channel

Zhang, Huayong; Wang, Zhong Yu; Dai, Liming; Xu, Weigang

doi:10.1115/1.4029608

Cited by 13 publications

(6 citation statements)

References 17 publications

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“…The turbulence intensities pattern in both vegetated and non-vegetated channels represent declines in directions of the flow. Study by Zhang et al [22] also resulted in the same manner as for vegetated unvarying bedforms.…”

Section: Resultsmentioning

confidence: 85%

The Hydrodynamic Characteristics for Vegetative Channel With Gravel Bed Dunes

2022

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Aquatic plants are known to provide flow resistance and impact the turbulence intensity and turbulent kinetic energy within the vegetated area. This paper further investigates the impact of both vegetation and dunes in open channels to the hydrodynamic characteristic of flow. Emergent vegetations were built from rigid wooden rod in staggered arrangement with 0.5% vegetations density were applied in the flume. Experiments were conducted with flow rate of 0.0058 m3/s throughout the experiments. Dunes were constructed from gravel of 2 mm size diameter in the shape of standing waves of three different lee slope angles of 3⁰, 6⁰ and 9⁰. Flow velocities are measured by using a velocimeter to get the raw data for the three-dimensional flow velocity in the x, y, and z directions. The velocities data were then analysed to calculate the mean velocity, turbulence intensity and turbulent kinetic energy. Experimental results showed that, for all three lee slope angles presented higher flow velocity in the vegetated channel compared to the non-vegetated channel. It was also found that greater lee slope angle dunes generate higher velocity for both channels with and without vegetation. Higher turbulence intensity can be found near the bed area and greater turbulence intensity also shown in the positive slope of a dunes compared to negative slope area. Higher turbulent kinetic energy values were recorded within the vegetated channel compared to the non-vegetated channels.

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Section: Resultsmentioning

confidence: 85%

The Hydrodynamic Characteristics for Vegetative Channel With Gravel Bed Dunes

2022

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“…As demonstrated by previous studies, vegetation density alters the characteristic length and time scales of energetic motion in open channel, the standard boundary-layer flows could also be shifted to canopy flows gradually with increasing vegetation density (Poggi et al, 2004), In fact, higher vegetation densities are generally used in the practices of river restorations to produce better ecological and environmental benefits (Nikora et al, 2013). Based on the comprehensive considerations on previous study (Velasco et al, 2003, Zhang et al, 2015a, field investigations and the reality of punched plates, a relatively dense vegetation density of 202 stems/m 2 is used in the present research.…”

Section: Methodsmentioning

confidence: 86%

“…For the purposes of ecological restoration and pollutant reduction, aquatic vegetation planting and management with different configurations have become common approaches in recent years (Zhou et al, 2006;Callow, 2012;Lama et al, 2021). For the rigid vegetation, due to the additional vegetal retardance, it has been noticed that vegetation planted in rivers may raise the water depth and reduce flow velocity, and therefore increase the potential risk of flooding or sediment silting (Zhang et al, 2015a;Friberg et al, 2017). However, the complexity of the combinations of hydraulic and vegetation conditions hindered the development the determination of the alternations of flow state due to vegetation block (Stone and Shen, 2002;Yagci et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Effects of vegetation height and relative submergence for rigid submerged vegetation on flow structure in open channel

Wang

Zhang

et al. 2022

Earth sci. res. j.

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In this research, the vegetation height and a concept of relative submergence are adapted to experimentally investigate the effects of rigid submerged vegetation on flow structure. The results reveal that the relative submergence presents decreasing trend along the submerged vegetation section and the average relative submergence follows a power functional decreasing relationship regarding to the increase of vegetation height. After the exit of vegetation block, the water depths for the vegetated cases resume to the level and trend of the case without vegetation. The differences between the maximum and minimum water depths for the submerged cases follow a linear relationship with vegetation height and a negative power functional relationship with the average relative submergence, with which, the raised water depths due to rigid submerged vegetation can be predicted under similar hydraulic and vegetation conditions to the present research. Due to the retardance of vegetation block, the differences between the maximum and minimum flow velocities increase with the vegetation height as the maximum values change slightly and the minimum values decrease continuously. The findings of the research may improve the comprehensive understandings of open channel hydraulic behaviors affected by rigid submerged vegetation and give some guidance to the river ecological restorations.

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“…Anisotropy analysis showed that a one-dimensional turbulence is dominant in a partly vegetated channel. Zhang et al [26] studied the effect of vegetation density on flow turbulence characteristics and Reynolds shear stress in a partly vegetated channel. A series of experiments were carried out in a rectangular channel of 30 m length (facilitates the generation of gradual varied flow), 1.3 m width, and 0.8 m depth.…”

Section: Introductionmentioning

confidence: 99%

Flow Characteristics in Partly Vegetated Channels: An Experimental Investigation

Ben Meftah,

Bhutto,

De Padova

et al. 2024

Water

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In this study, we attempt to experimentally investigate the flow turbulence structure in a partly vegetated channel. To achieve the objective of this study, we conducted extensive measurements of flow velocities within and outside the vegetated area, where the flow is fully developed. The experiments were conducted in a very large channel at the Coastal Engineering Laboratory of the Department of Civil, Environmental, Building Engineering and Chemistry at the Polytechnic University of Bari, Italy. The instantaneous three flow velocity components were accurately measured using a 3D-Acoustic Doppler Velocimeter (ADV)-Vectrino system at high frequency. Flow behaviors through the vegetated area, at the interface, and in the unobstructed area were analyzed via time-averaged velocities, turbulence intensity, correlation properties, spectral analysis, and vortex identification. Experimental results showed the development of three distinct characteristic flow zones: (i) a vegetated area of low streamwise velocity, high turbulence intensities, dominant inward interactions, and more intense power spectrum, (ii) a shear layer zone of increasing streamwise velocity, more enhanced transverse flow motion, exponential decrease in turbulence intensities, and frequent ejection and/or outward interaction events, and (iii) a free-stream zone of higher and almost constant streamwise velocity, lower turbulence intensities, frequent sweep and/or inward interaction events, and less intense streamwise power spectrum. The results brought further insights into the flow behaviors in these characteristic flow zones. The extensive and detailed measured data can provide a basis for improving and calibrating numerical simulations of partly vegetated channels.

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Influence of Vegetation on Turbulence Characteristics and Reynolds Shear Stress in Partly Vegetated Channel

Cited by 13 publications

References 17 publications

The Hydrodynamic Characteristics for Vegetative Channel With Gravel Bed Dunes

The Hydrodynamic Characteristics for Vegetative Channel With Gravel Bed Dunes

Effects of vegetation height and relative submergence for rigid submerged vegetation on flow structure in open channel

Flow Characteristics in Partly Vegetated Channels: An Experimental Investigation

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