Flow behaviour in a multi‐layered vegetated floodplain region of a compound channel

Barman, Jyotirmoy; Kumar, Bimlesh

doi:10.1002/eco.2427

Cited by 9 publications

(5 citation statements)

References 65 publications

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“…These two turbulent shear components, which are operating in opposite streamwise and transverse directions on the plane of sediments, are

τ_{Z - X}

and

τ_{Z - Y}

, respectively. The streamwise Reynolds shear stress distribution

τ_{Z - X} = - ρ ((), \bar{u' w'})

(Barman & Kumar, 2022a; Pu, 2021) in the riverbank segment is given in Figure 6. Figure 7 illustrates the riverbank's transverse Reynolds shear stress contours where u ′ and w ′ are obtained from the experimental readings using ADV, as mentioned in Section 2.2 above.…”

Section: Resultsmentioning

confidence: 99%

“…It was sowed as multiple seeds were placed in a straight‐line hole and watered, as shown in Figure 2(b). Such straight lines were placed at a distance of 9 cm to get sparse vegetation density based on the literature (J. Barman & Kumar, 2022a, 2022b; Mossa et al, 2017; Zong & Nepf, 2010). The vegetation was supported for 15 days when they achieved a height of 0.3 m. It was now double the height of the riverbank and could be used as flexible emergent vegetation, as shown in Figure 2(d,e).…”

Section: Methodsmentioning

confidence: 99%

“…Such straight lines were placed at a distance of 9 cm to get sparse vegetation density based on the literature (J. Barman & Kumar, 2022a, 2022bMossa et al, 2017;Zong & Nepf, 2010). The vegetation was supported for the average length of roots to be more than 0.15 m, as shown in experiments.…”

Section: Instrumentation and Data Recordingsmentioning

confidence: 99%

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The riverbank vegetation for mitigating the adverse effects of sediment dredging

Arora,

Kumar

2024

Ecohydrology

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Sediment dredging has been an ever‐growing issue, especially in developing nations with high demand for concrete filler material. River systems are adversely affected by sediment mining, resulting in decreased stability of the riverbed and riverbanks. Nature‐based solutions for riverbank erosion have been a research topic that has led to the proposal of vegetation on the riverbanks. However, little is known about the extent of riverbank vegetation required to negate the devastating effects of sediment mining because dense vegetation severely affects the flow structure and becomes a waste trap. This experimental study uses sparsely dense, flexible, and bladed vegetation to study the annulment effects of vegetation against the existing mining pit. Near‐bed turbulence and sediment transport have increased in the test section in the presence of a mining pit. The increase in near‐bed streamwise and transverse Reynolds shear stresses helped us understand the increased sediment movement in streamwise and lateral directions. The morphology of the test section showed increased riverbed erosion at the beginning of the test segment. The entire cross‐section was levelled at the end of the test section, and aggradation was downstream of the test segment. In contrast, in the vegetated riverbank case, the initial profile of the bank was almost unchanged for the same discharge of flow and upstream sand pit. The sparse vegetation overperformed the intended negation effects. This study establishes that sparse vegetation would perform better in maintaining the channel morphology, which otherwise in dense vegetation would have faced a high erosion rate in the main channel while giving the same protection to the riverbanks.

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“…These two turbulent shear components, which are operating in opposite streamwise and transverse directions on the plane of sediments, are

τ_{Z - X}

and

τ_{Z - Y}

, respectively. The streamwise Reynolds shear stress distribution

τ_{Z - X} = - ρ ((), \bar{u' w'})

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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The riverbank vegetation for mitigating the adverse effects of sediment dredging

Arora,

Kumar

2024

Ecohydrology

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“…Recent investigations concentrate mainly on the hydraulics of different forms of vegetation. Different materials have been used to imitate aquatic vegetation such as rods and wooden cylindrical dowels for rigid vegetation (Cheng & Nguyen, 2011; Panigrahi & Khatua, 2015; Sharil et al, 2016) with uniform arrays of staggered or aligned (Chatelain & Proust, 2021; Dupuis et al, 2016; Martino et al, 2012) or randomly (Ricardo et al, 2014; Tanino & Nepf, 2008) or partially vegetated open channel (Buckman, 2013; Devi et al, 2019; White & Nepf, 2008) or multi‐layer vegetation (Barman & Kumar, 2022; Liu et al, 2010), flexible vegetation like blades or strips (Chen et al, 2011; Nepf & Vivoni, 2000), natural vegetation (Carollo et al, 2005; Devi et al, 2017; Stephan & Gutknecht, 2002), combined layer of flexible vegetation in emergent and submerged condition (Li et al, 2014), and various combinations (Freeman et al, 2000; Järvelä, 2002). In comparison with studies related to flexible vegetation types, there have been more studies in channels with rigid vegetation (Wilson et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation of 3D flow properties around emergent rigid vegetation

Kumar

Sharma

2022

Ecohydrology

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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.

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“…They reported that the effort of the secondary flow is significant in the redistribution of longitudinal momentum in the compound open channel flows. Barman and Kumar [17] physically collected the turbulent measurements in the heterogeneous canopy within the floodplain area of compound open channels. The differences of flow properties were identified, compared to the cases with homogeneous floodplain vegetation.…”

Section: Introductionmentioning

confidence: 99%

Large Eddy Simulation of Compound Open Channel Flows with Floodplain Vegetation

Zeng

Bai

Zhou

et al. 2022

Water

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Floodplain vegetation is of great importance in velocity distribution and turbulent coherent structure within compound open channel flows. As the large eddy simulation (LES) technique can provide detailed instantaneous flow dynamics and coherent turbulent structure predictions, it is of great importance to perform LES simulations of compound open channel flows with floodplain vegetation. In the present study, a wall-modeled large eddy simulation (WMLES) method was employed to simulate the compound open channel flows with floodplain vegetation. The vegetation-induced resistance effect was modeled with the drag force method. The WMLES model, incorporating the drag force method, was verified against flume measurements and an analytical solution of vegetated open channel flows. Numerical simulations were conducted with a depth ratio of 0.5 and four different floodplain vegetation densities (frk = 0, 0.28 m−1, 1.13 m−1 and 2.26 m−1). The main flow velocity, secondary flow, bed shear stress and vortex coherent structure, based on the Q criterion, were obtained and analyzed. Based on the numerical results, the influences of floodplain vegetation density on the flow field and turbulent structure of compound open channel flows were summarized and discussed. Compared to the case without floodplain vegetation, the streamwise velocity in the main channel increased by 10.8%, 19.9% and 24.4% with the frk = 0.28 m−1, 1.13 m−1 and 2.26 m−1, respectively. The results also indicated that, when the floodplain vegetation density increased, the following occurred: the velocity increased in the main channel, while the velocity decreased in the floodplain; the transverse momentum exchange was enhanced; and the strip structures were more concentrated near the junction area of compound open channel flows.

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Flow behaviour in a multi‐layered vegetated floodplain region of a compound channel

Cited by 9 publications

References 65 publications

The riverbank vegetation for mitigating the adverse effects of sediment dredging

The riverbank vegetation for mitigating the adverse effects of sediment dredging

Experimental investigation of 3D flow properties around emergent rigid vegetation

Large Eddy Simulation of Compound Open Channel Flows with Floodplain Vegetation

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