Turbulence at water-vegetation interface in open channel flow: Experiments with natural-like plants

Caroppi, Gerardo; Västilä, Kaisa; Järvelä, Juha; Rowiński, Paweł M.; Giugni, Maurizio

doi:10.1016/j.advwatres.2019.03.013

Cited by 66 publications

(55 citation statements)

References 57 publications

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“…Data were collected in an experimental flume mimicking a main channel with a vegetated bank consisting of understory grasses and emergent flexible woody vegetation. Measurements conducted in this study were collected in parallel with a study on the turbulent flow induced by flexible vegetation between the main channel-floodplain interface [30]. Those data and analyses for example on the horizontal moving coherent flow structures support the explanations on the suspended sediment transport and net deposition given in the present study.…”

Section: Introductionsupporting

confidence: 75%

“…There are notable differences in the description of the lateral mixing layer between rigid and flexible foliated vegetation caused, for example, by the lateral waving of the vegetated interfaces [30]. Leafless plant stems can be considered rigid cylinders and parameterized following a rigid cylinder model; e.g., [2,3,8,9].…”

Section: Vegetated Conditionmentioning

confidence: 99%

“…Leafless plant stems can be considered rigid cylinders and parameterized following a rigid cylinder model; e.g., [2,3,8,9]. Flexible, foliated floodplain vegetation has been modelled through approaches taking into account the reconfiguration and streamlining, e.g., [7,30]. In the rigid cylinder case, the drag force is assumed to scale with the velocity squared F ∝ U 2 , whereas in the flexible case, the drag force scales with F ∝ U 2+χ , where χ is the reconfiguration parameter which is species-specific [7,14].…”

Section: Vegetated Conditionmentioning

confidence: 99%

“…In the HQ flow conditions, the foliated plant stems were bent and the leaves strongly reconfigured. The vegetation drag-density parameter C D a was 0.205 and 0.181 for the leafless MQ-L and HQ-L cases, and 1.432 and 0.485 for the foliated MQ-F and HQ-F cases, respectively [30]. The total drag density induced by the vegetation was computed from a momentum balance, deep within the vegetation [30].…”

Section: Vegetated Cross-section and Characteristicsmentioning

confidence: 99%

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The Interplay between Flow Field, Suspended Sediment Concentration, and Net Deposition in a Channel with Flexible Bank Vegetation

Box

Västilä

Järvelä

2019

Water

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This paper investigates the interplay between the flow, suspended sediment concentration (SSC), and net deposition at the lateral interface between a main channel and riverbank/floodplain vegetation consisting of emergent flexible woody plants with understory grasses. In a new set of flume experiments, data were collected concurrently on the flow field, SSC, and net deposition using acoustic Doppler velocimeters, optical turbidity sensors, and weight-based sampling. Vegetation largely affected the vertical SSC distributions, both within and near the vegetated areas. The seasonal variation of vegetation properties was important, as the foliage strongly increased lateral mixing of suspended sediments between the unvegetated and vegetated parts of the channel. Foliage increased the reach-scale net deposition and enhanced deposition in the understory grasses at the main channel–vegetation interface. To estimate the seasonal differences caused by foliation, we introduced a new drag ratio approach for describing the SSC difference between the vegetated and unvegetated channel parts. Findings in this study suggest that future research and engineering applications will benefit from a more realistic description of natural plant features, including the reconfiguration of plants and drag by the foliage, to complement and replace existing rigid cylinder approaches.

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Section: Introductionsupporting

confidence: 75%

Section: Vegetated Conditionmentioning

confidence: 99%

Section: Vegetated Conditionmentioning

confidence: 99%

Section: Vegetated Cross-section and Characteristicsmentioning

confidence: 99%

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The Interplay between Flow Field, Suspended Sediment Concentration, and Net Deposition in a Channel with Flexible Bank Vegetation

Box

Västilä

Järvelä

2019

Water

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“…The global flow resistance generated in vegetated channels could be estimated by employing many models, also known as "resistance predictors" [4]. Each model has been derived under distinct hydraulic (laboratory flumes or real vegetated channels) and vegetative (real or artificial riparian plants) conditions [1,6,7]. Among others, the Baptist et al [8] and the Stone and Shen [9] resistance models (hereinafter referred to as Bp and S&S [8,9]) have been validated for real riparian vegetation, considering both emergent and submerged vegetative conditions, depending on the ratio between the water level (h) and the plants height above the vegetated channel bottom (h v ).…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Flow Resistance Models Based on Field Experiments in a Partly Vegetated Reclamation Channel

et al. 2020

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This study presents a methodology for improving the efficiency of Baptist and Stone and Shen models in predicting the global water flow resistance of a reclamation channel partly vegetated by rigid and emergent riparian plants. The results of the two resistance models are compared with the measurements collected during an experimental campaign conducted in a reclamation channel colonized by Common reed (Phragmites australis (Cav.) Trin. ex Steud.). Experimental vegetative Chézy’s flow resistance coefficients have been retrieved from the analysis of instantaneous flow velocity measurements, acquired by means of a downlooking 3-component acoustic Doppler velocimeter (ADV) located at the channel upstream cross section, and by water level measurements obtained through four piezometers distributed along the reclamation channel. The main morphometrical vegetation features (i.e., stem diameters and heights, and bed surface density) have been measured at six cross sections of the vegetated reclamation channel. Following the theoretical assumptions of the divided channel method (DCM), three sub-sections have been delineated in the reference cross section to represent the impact of the partial vegetation cover on the cross sectional variability of the flow field, as observed with the ADV measurements. The global vegetative Chézy’s flow resistance coefficients have been then computed by combining each resistance model with four different composite cross section methods, respectively suggested by Colebatch, Horton, Pavlovskii, and Yen. The comparative analysis between the modeled and the experimental vegetative Chézy’s coefficients has been performed by computing the relative prediction error (εr, expressed in %) under two flow rate regimes. Stone and Shen model combined with the Horton composite cross section method provides vegetative Chézy’s coefficients with the lowest εr.

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

Wang¹,

Liu²,

Feng-yang³

et al. 2021

Ecohydrology

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The vertical distribution of longitudinal velocity and the turbulence structure of open channel flows with natural‐like reedy emergent vegetation were investigated in this study. The natural‐like reedy vegetation consisted of a basal stem and flexible blades with shape and reconfiguration behaviour comparable with those found in actual riparian areas. The 3D velocity field was measured using an acoustic Doppler velocimeter. The vertically non‐uniform distribution of the frontal area could dramatically affect the exchange of mass and momentum between emergent vegetation and their surroundings. The average time velocity profile varied inversely with the frontal area. The high velocity gradient appearing at the middle section of the zone with frontal area varied considerably. The structures of vortices and vertical transport were analysed using spectral analysis and conditional sampling to identify the prominent vortical structures and their contribution to momentum transport. Spectral analysis suggested that the stem‐scale vortices set by stem spacing where the vertical frontal area had no clear change were dominant, and shear‐layer vortices where vertical frontal area dramatically changed cannot be disregarded. Quadrant analysis showed that inward and outward interactions were the dominant contributors to Reynolds stress, excluding the zones approaching the channel boundary and the vertical frontal area that dramatically changed. A four‐layer model was developed to predict the vertical distribution of longitudinal velocity with a newly established profile of local drag coefficient. The predicting results agreed well with the experimental data.

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Turbulence at water-vegetation interface in open channel flow: Experiments with natural-like plants

Cited by 66 publications

References 57 publications

The Interplay between Flow Field, Suspended Sediment Concentration, and Net Deposition in a Channel with Flexible Bank Vegetation

The Interplay between Flow Field, Suspended Sediment Concentration, and Net Deposition in a Channel with Flexible Bank Vegetation

Evaluation of Flow Resistance Models Based on Field Experiments in a Partly Vegetated Reclamation Channel

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

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