Experimental and Numerical Study on Impact of Double Layer Vegetation in Open Channel Flows

Rahimi, Hamidreza; Tang, Xiaonan; Singh, Prateek Kumar

doi:10.1061/(asce)he.1943-5584.0001865

Cited by 28 publications

(15 citation statements)

References 35 publications

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“…This is preferable to use wooden rods that at such a small diameter could break or bend significantly during the experimentation. This design choice is consistent with other authors who also used steel cylinders (Huai, Zeng, Xu, & Yang, 2009), while others have used plastic dowels (Huai, Wang, Hu, Zeng, & Yang, 2014) or metal rods (Rahimi, Tang, & Singh, 2019), for vegetation modeling by keeping the geometrical similarity of the physical models. The staggered configuration of vegetation offered more resistance than grid configuration (Takemura & Tanaka, 2007) (Bokaian & Geoola, 1984).…”

Section: Vegetation Conditionssupporting

confidence: 80%

Experimental investigation of flood energy reduction through vegetation at various angles

Ahmed

Valyrakis

Ghumman

et al. 2021

River Research & Apps

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The efficiency of flow energy reduction past emergent vegetation has been typically studied assuming a right angle of the vegetated corridor to the flow direction. However, in many real-world cases the riparian zones of natural, restored, or engineered rivers and waterways, are found at an oblique angle to the flood flow direction. In the current study, the effect of vegetation angle with respect to the flow direction is investigated experimentally in an open channel rectangular flume. The experiments are conducted under a range of subcritical steady flow conditions, with varying Froude number (Fr o ). The vegetation cover is placed at various angles to the flow direction (90 , 45 , and 30 ), for a sparse and intermediate vegetation density, defined from the ratio of spacing of each vegetation element in the cross stream direction (B), and the diameter of vegetation element (d) (B/d = 2.13 and 1.09, respectively). Detailed water surface profiles are obtained for all those cases, demonstrating a considerable backwater rise, increasing with increasing vegetation density, Froude number, and flow approach angle. The energy reduction decreased by increasing the Froude number for the perpendicular (90 ) and increased for oblique vegetation (45 and 30 ). For the perpendicular vegetation, the average energy reduction rate for sparse (90VS) and intermediate (90VI) vegetation densities are 25.44% and 31.44%, respectively. The range of average energy reduction for sparse vegetation at 45 (45VS) and at 30 (30VS) are 18.3-19.8% and 18.7-19.7%, respectively. Similarly, range of average energy reduction for intermediate vegetation at 45 (45VI) and at 30 (30VI) are 21.4-22% and 18.8-22%, respectively.

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Section: Vegetation Conditionssupporting

confidence: 80%

Experimental investigation of flood energy reduction through vegetation at various angles

Ahmed

Valyrakis

Ghumman

et al. 2021

River Research & Apps

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“…The characteristics of flow through vegetation may be interpreted using different mechanisms over the flow depth (Nikora et al, 2013;Huai et al, 2014;Rahami et al, 2020).Thus, the velocity profile can be modelled separately in a layer with each phenomenon described (Tang & Ali, 2013;Tang, 2018Tang, , 2019aTang, , 2019bSingh et al, 2019). The flow structure in vegetated channels has also been investigated through numerical modelling (e.g., Lopez & Garcia, 2001;Neary, 2003;Zeng & Li, 2014) and CFD simulation using FLUENT (Souliotis & Prinos, 2011;Anjum et al, 2018;Anjum & Tasnka, 2019;Rahimi et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

“…To understand the influence of multiple-layered vegetation on the flow structure, some laboratory studies were carried out in an open-channel with the bed fully covered by a mixing array of short and tall vegetation (e.g., Liu et al, 2008;Anjum et al, 2018;Tang et al. 2019;Rahimi et al. 2019Rahimi et al.…”

Section: Introductionmentioning

confidence: 99%

Impact of Partially Covered Vegetation on the Lateral Velocity Distribution of Open Channel Flow

Tang¹,

Hu²

2021

GEP

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The vegetation affects the flow process and water environment, thus drawing increasing attention to river environment management. Previous research is mainly focused on flow through vegetation in a channel with fully covered single-layer vegetation. However, in natural rivers, different heights' vegetation often co-exists along one or two sides of a river. This paper experimentally studies how the flow velocity distribution is affected by the two different-layered vegetation allocated along two sides of an open-channel. The vegetation was simulated by dowels of two heights, 10 cm and 20 cm, and arranged in a parallel pattern along two sides of a flume under partially submerged conditions. The velocities along a cross-section were measured by Acoustic Doppler Velocimetry (ADV). The results of lateral velocity distribution show that a strong shear layer exists between vegetation and non-vegetation zones, indicating the retarding effect of vegetation. Meanwhile, as the flow depth increases, the relative velocity in the free flow zone decreases compared with that in the vegetated region, indicating that vegetation resistance to the flow decreases as increasing depth under the same vegetation configuration. These findings would help understand the role of multi-layered vegetation in riparian management.

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“…For understanding the flow structure of channels with mixing-layered vegetation, some experimental studies were done in an open channel fully covered with a coexistence of tall and short vegetation (e.g. [20][21][22][23]). Most recently, Tang et al [24][25][26] conducted some experimental studies on the flow characteristics of a channel with two-layered vegetation that covered part of the channel bed.…”

Section: Introductionmentioning

confidence: 99%

Discharge and velocity variation of flows in open channels partially covered with different layered vegetation

et al. 2021

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The role of vegetation in the natural environment has drawn great interest recently. The vegetation can change the velocity distribution due to its additional resistance on the flow, consequently affecting the nutrient and pollutant transport, and the habitats. Due to the complexity of flow and vegetation interaction, many previous researchers have studied the flow structure of channels with uniform vegetation. Few studies have been done on the flow of open channels partially covered vegetation of different heights on one side of the channel, which commonly exists in natural rivers. Through novel experiments for such a vegetated flow, this paper shows the influence of different layered vegetation on the velocity profile and discharge, which indicates that the velocity in the vegetation zone is significantly smaller than that in the free-flow zone and that the velocity profiles in the short and tall vegetation zones are very different. The flow through the free-flow zone is dominant (about 75%) despite its half width, and its discharge percentage slightly decreases as increasing flow depth.

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Experimental and Numerical Study on Impact of Double Layer Vegetation in Open Channel Flows

Cited by 28 publications

References 35 publications

Experimental investigation of flood energy reduction through vegetation at various angles

Experimental investigation of flood energy reduction through vegetation at various angles

Impact of Partially Covered Vegetation on the Lateral Velocity Distribution of Open Channel Flow

Discharge and velocity variation of flows in open channels partially covered with different layered vegetation

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