Turbulent anisotropy and coherent structures in flow through a symmetric compound channel with emergent floodplain vegetation

Physics of Fluids, Год журнала: 2025, Номер 37(1)

Опубликована: Янв. 1, 2025

This experimental study advances understanding of the impact homogeneous grass (HG), shrub, and mixed (heterogeneous) vegetation (MV) on floodplains (FPs) flow dynamics within a symmetric compound channel. Velocity measurements were conducted using an Acoustic Doppler Vectrino Profiler in main channel (MC), slope region (SR), FP to compute depth-averaged mean streamwise velocity, Reynolds stress anisotropy tensors, coherent structures. The analysis revealed 54% increase velocity at MC centerline with MV compared no (NV) case, marking highest observed among all scenarios. showed that turbulence dominated both SR, particularly MV, reflecting enhanced momentum exchange due vegetation. anisotropic invariant map demonstrated shift from one-dimensional two-dimensional (2D) states formation cigar-shaped structures, especially SR. was attributed increased resistance. Quadrant intensified bursting events, enhancing sediment transport near-bed NV case. At free surface, outward interactions more frequent than inward interactions, indicating upward water movement. Higher vortex frequency energy dissipation SR vegetated confirmed presence quasi-2D facilitating breakdown larger vortices into smaller ones. These findings provide critical insights for river system management, emphasizing vegetation's role altering transport.

Язык: Английский

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Shallow turbulent mixing layers in open-channel flows

Environmental Fluid Mechanics, Год журнала: 2025, Номер 25(1)

Опубликована: Янв. 15, 2025

Abstract A mixing layer (ML) forms when two streams of different speeds or densities merge. MLs are ubiquitous in nature and can be often observed the atmosphere, ocean, rivers, canals, lakes reservoirs. This review paper focuses on turbulent developing open-channel flows vertical size ML is smaller than its streamwise spanwise dimensions. Such referred to as shallow (SMLs). The SMLs involve large-scale features such quasi-two-dimensional coherent structures with a bed-normal axis, streamwise-oriented vortices, secondary currents, gravity bed-induced large- very-large-scale motions. Considering various types SMLs, we distinguish driven by (i) inhomogeneity hydrodynamic parameters, (ii) lateral changes flow resistance, (iii) heterogeneity fluid density. As associated largely control transverse exchanges substances (e.g., sediments, pollutants, nutrients) heat, thermal also addressed. Then, commonalities differences among identified. concluded suggestions future research efforts for advancing knowledge capabilities their predictions control.

Язык: Английский

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Turbulence in a compound channel with the combination of submerged and emergent vegetation

Physics of Fluids, Год журнала: 2022, Номер 34(4)

Опубликована: Апрель 1, 2022

Floodplain vegetation is heterogeneous with varying heights and spacing. Laboratory studies concerning compound channels mixed submerged emergent are scarce. This paper attempts to address the difference in flow behavior when it encounters single-layered or a combination of both. Two different sets uniform non-uniform setups considered. Vegetation cases submerged, emergent, considered for each set. The velocity floodplain region fully higher than that combined because less frontal area provided by vegetation. Reynolds shear stress also lower depth main channel compared height vegetation, especially setup. Turbulent anisotropy octant analysis studied detail get further insight into setups. anisotropic invariant map function F reveal section 67% case has greater tendency approach two-dimensional turbulence other Octant study shows internal sweep highest 34% setup lowest 100%

Язык: Английский

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Turbulence structure and bank erosion process in a dredged channel

River Research and Applications, Год журнала: 2023, Номер 39(4), С. 613 - 628

Опубликована: Янв. 6, 2023

Abstract Riverbank erosion has significant geomorphological as well anthropogenic consequences. The impacts include form changes such lateral channel migration, meanders, expansion, etc. effects the threat to floodplain human habitation, agricultural land, and stability of instream hydraulic structures buried pipelines. Channel dredging for extraction sand gravel seen a multi‐fold rise in last few decades. Therefore, riverbank response mining gains importance river basin management. Sandpits dredged riverbeds can significantly impact downstream stability. In order assess these impacts, we conducted series experiments at laboratory scale recirculating water flume. Three slopes, 25° (gentle), 31° (equal angle repose bank sediments), 40° (steeper than repose), were tested along with sandpit. Remarkable turbulence structure flow found due pit. Pit excavation directly fluvial characteristics riverbank. action increases Reynolds shear stress fields near‐bank flow, which causes progressive berm toe. erosivity main also leads degradation, exposed height slope. generation stronger ejection bursts provide mechanism sediment mobility erosion. hydro morphological was analysed, process understandings are presented paper.

Язык: Английский

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Hydrodynamics in channels with partial vegetation cover: Investigating the effects of homogeneous and heterogeneous vertical vegetation distribution

Advances in Water Resources, Год журнала: 2024, Номер 185, С. 104642 - 104642

Опубликована: Фев. 1, 2024

Язык: Английский

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Flow in multi-layered vegetated compound channels with different bank slopes

Physics of Fluids, Год журнала: 2023, Номер 35(3)

Опубликована: Фев. 20, 2023

Bank angle and floodplain vegetation emergence determine the flow nature in a compound channel. Two sets of 45° 90° bank channel is considered present work. Each set considers three cases arrangements: no vegetation, multi-layered fully submerged, partially emergent. The characteristics like velocity, Reynolds shear stress (RSS), turbulent kinetic energy (TKE) do not vary much cross section absence vegetation. However, with slopes nearby region are affected most as it acts an intermediary between main floodplain. An analysis anisotropic invariant map shows dominance transverse component compared to velocity around higher for steep (90°) gradual slope (45°) streamwise RSS bursting events also show magnitude near bed sloping region. This indicates instability banks slopes. increase affects TKE greater vulnerability presence emergence. From hydraulic engineering perspective, this study will be helpful field understanding failure ways maintain their stability.

Язык: Английский

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Numerical modeling of turbulent flow interactions with vegetation in channels with fixed beds

Modeling Earth Systems and Environment, Год журнала: 2024, Номер 10(3), С. 4337 - 4360

Опубликована: Май 8, 2024

Язык: Английский

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Effect of downward seepage on turbulence and morphology in mobile boundary sinuous channel

Physics of Fluids, Год журнала: 2022, Номер 35(1)

Опубликована: Дек. 22, 2022

The porous boundary of alluvial channels allows water to interact with the surrounding groundwater. With reduction in groundwater level, transfer from main channel is significant and referred as downward seepage. action seepage causes morphological alteration along sinuous channel. Laboratory experiments were conducted for no-seepage conditions study effect on turbulence bed morphology rectangular trapezoidal channels. deformation streambed bank showed remarkable alterations Downward caused excess sediment transport showing high erosion banks streambed. increased flow rate seepage, prominent depositionalzones near inner region zones outer bend observed cross section. Sinuous section less change side slope was almost equal angle repose sand. However, application has lowered elevation, indicating transport. Mean streamwise velocity at center an average percentage increase 26% about 20% Reynolds shear stress estimated bed, momentum flux. Higher indicated which results downstream

Язык: Английский

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Turbulence structure in an experimental compound channel with varying coverage of riparian vegetation on the floodplain

Journal of Hydrology, Год журнала: 2023, Номер 620, С. 129378 - 129378

Опубликована: Март 11, 2023

Язык: Английский

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Conditional statistics of Reynolds stress in open channel flows with modeled canopies of homogeneous and heterogeneous density

Physics of Fluids, Год журнала: 2023, Номер 35(3)

Опубликована: Фев. 18, 2023

The flow structures under the effects of heterogeneous canopies have been shown to be significantly different from those homogeneous canopies. purpose this study is investigate how changes in density and uniformity canopy affect turbulent characteristics a partially vegetated channel. A comparative experiment conducted, including two cases with densities one case consisting alternating sparse dense vegetation patches. While lateral profiles Reynolds stress, magnitudes quadrant motions, high-order moments velocity fluctuations present high similarity within shear layer, variations both markedly turbulence at interface between main results show that heterogeneity enhances momentum exchange promotes penetration stress-driven into patch while inhibiting its patch. An analogy can drawn sufficient rough-wall boundary layers based on statistics layer. Furthermore, effect increased corresponds well decreased wall roughness. By using cumulant expansion method, assumption structural wall-bounded flows found applicable considered study.

Язык: Английский

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