Turbulence structure and longitudinal velocity distribution of open channel flows with reedy emergent vegetation

Wang, Jiasheng; Liu, Xiaoguang; Feng-yang, Min; Dai, Juan

doi:10.1002/eco.2352

Cited by 18 publications

(5 citation statements)

References 73 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…On the one hand, the vegetation may considerably increase flow resistance, slowing down the flow and raising the water levels, so increasing the risk of floods. On the other hand, by changing in velocity distribution and turbulent structures in vegetated channels (Li et al, 2015;Nikora et al, 2013;Wang et al, 2022;Yang et al, 2019), vegetation promotes sediment deposition (Wu and He, 2009), reduces bed erosion and increases bank stability (Vargas-Luna et al, 2016). Furthermore, vegetation is known to provide habitats for aquatic and terrestrial wildlife, beautify the environment, and permeate pollutants (Huai et al, 2018;Liu et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Flow resistance of emergent rigid vegetation in steady flow

Wang,

Liu,

Sun

et al. 2024

Journal of Hydrology and Hydromechanics

View full text Add to dashboard Cite

Enhanced understanding of flow resistance in open channels with emergent vegetation is essential for flood management and river ecosystem restoration. The presence of vegetation can significantly alter bed resistance, leading to a challenge in accurately predicting flow discharge, water levels, sediment transport, and bed deformation. Previous studies on vegetated flows have focused on vegetation resistance, on which the impact of vegetation has been ignored or poorly estimated. This study proposes a new analytical model, built upon the momentum conservation law, to predict flow resistance to vegetated zones in a plain bed without bed forms, explicitly quantifying bed resistance and vegetation resistance in a corollary manner. The proposed model is benchmarked against five typical sets of laboratory experiments. It is demonstrated that the present model using a modified logarithmic velocity distribution performs best, whereas that assuming a uniform velocity profile considerably overestimates the vegetation resistance and neglects the effect of vegetation on bed resistance. The ratio of bed resistance to the total resistance is shown to range between 5% and 40%, and it decreases with increasing vegetation density and decreases with water depth. Therefore, bed resistance cannot be ignored when modelling shallow water flow with sparsely distributed vegetation. It is also revealed that vegetation arrangements significantly affect flow resistance, and therefore a model incorporating the effect of vegetation arrangement performs better. Overall, the present model facilitates a viable and promising tool for quantifying flow resistance in emergent vegetated channels.

show abstract

Section: Introductionmentioning

confidence: 99%

Flow resistance of emergent rigid vegetation in steady flow

Wang,

Liu,

Sun

et al. 2024

Journal of Hydrology and Hydromechanics

View full text Add to dashboard Cite

show abstract

“…Flume experiments based on model vegetation, which is simulated by cylinder or strip arrays, have been employed for two decades (Ben Meftah & Mossa, 2016; Ghisalberti & Nepf, 2004; Huai et al, 2015; Liu et al, 2020; Nepf & Vivoni, 2000; Nezu & Onitsuka, 2001; Shan et al, 2020; Wang, Liu, et al, 2021; Yan et al, 2015; Yan et al, 2016; Yan et al, 2020). By changing the flow depth, submerged and emergent vegetation canopies can be modelled (Chang et al, 2020; Li et al, 2014; Yan et al, 2016), and by changing the obstruction ratio of the flume, partially distributed and fully distributed vegetation canopies can be modelled (Xu et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Hydrodynamic adjustment subject to a submerged canopy partially obstructing a flume: Implications for junction flow behaviour

Yan

Jia

Fang³

et al. 2023

Ecohydrology

View full text Add to dashboard Cite

The scenario of a submerged canopy partially obstructing a channel is common in the natural aquatic flow environment. This study experimentally evaluated the flow adjustment performance and vertical flow structure adaptive to a submerged partially distributed canopy. The experimental results showed that the canopy interior velocity adjustment distance for submerged partially distributed canopies was comparable with that for emergent ones. However, it was smaller than that for submerged fully distributed canopies but comparable with that for emergent fully distributed ones. For the fully developed flow, the neighbouring open waters insignificantly impact the flow structure in the vegetation region (VR), where the mixing-layer flow behaviour arising from the generation of the vertical coherent vortices was maintained. The vertical mixing-layer flow behaviour characterised by pronounced vertical Reynolds shear stress transversely extended into the nonobstructed region, suggesting that the canopy-side waters significantly impacted the neighbouring open flow. This effect decayed in the case of decreasing canopy density and as the location leaving the junction region (JR). Of importance was that near-bed velocity deflection occurred in the JR and was facilitated by canopy density. Vertically nonuniform distribution of transverse momentum exchange from horizontal coherent vortices due to bed depression can account for the near-bed velocity deflection. The gained knowledge allowed the development of a phenomenological model for understanding the vertical flow structure in partially vegetated channels.

show abstract

“…Aquatic plants play an important role in the beauty, ecological restoration, and flood controls in rivers, canals, and also impact the nutrients transmission, flow structures, and turbulence (Tsujimoto, 1999; Wang et al, 2021). Vegetation provides habitats for aquatic lives, to increase bank stability, reduce erosion, decrease turbidity, reduce floods, and permeate pollutants (Bennett et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

“…However, the flow velocity fluctuates more significantly; average flow velocity is higher when vegetation is parallel than staggered, and the averaged flow velocity is higher when vegetation is sparse than dense in upstream of vegetation area. Wang et al (2021) found that the flow velocity under the presence of emergent vegetation can be decreased. It is of great significance in flood control of rivers.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation of 3D flow properties around emergent rigid vegetation

Kumar

Sharma

2022

Ecohydrology

View full text Add to dashboard Cite

The condition of emergent or submerged vegetation plays a vital role in affecting the flow behaviour in open channels. To understand the flow processes in free surface flows under emergent rigid vegetation condition, an extensive experimental investigation is performed in a laboratory channel with staggered combination of emergent rigid vegetation. Three-dimensional velocities data are collected by ADV at various section and position of vegetated channel. The three-dimensional flow properties such as velocity distribution, turbulence intensity, turbulent kinetic energy, Reynolds shear stress in vegetation, and non-disturbed region are analysed and compared with the longitudinal and transverse length of vegetated zone. In the vegetation region, the longitudinal velocity in free stream region decreases as compared with nondisturbed region. However, the vertical velocity also decreases in free stream region except at the centre line of channel cross-section. Variations in velocity in the vegetation section were observed because of the local effect induced by the vegetation stems. Three-dimensional Reynolds shear stress and turbulent intensity were weaker in magnitude at vegetation region. The presence of vegetation reduces the longitudinal profile of flow velocity, Reynolds shear stress and turbulence intensities, which means that vegetation can be used as an effective tool to reduce the flow resistance.The turbulent kinetic energy, skewness and kurtosis are also evaluated and compared between the vegetated and non-vegetated zone. The outcomes of the results provide an important view to understand flow behaviour at immediately front and immediately behind of vegetation stem.

show abstract

Turbulence structure and longitudinal velocity distribution of open channel flows with reedy emergent vegetation

Cited by 18 publications

References 73 publications

Flow resistance of emergent rigid vegetation in steady flow

Flow resistance of emergent rigid vegetation in steady flow

Hydrodynamic adjustment subject to a submerged canopy partially obstructing a flume: Implications for junction flow behaviour

Experimental investigation of 3D flow properties around emergent rigid vegetation

Contact Info

Product

Resources

About