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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Turbulent Flow Structure in a Symmetric Compound Channel With Flexible Emergent Vegetation Over Floodplains

Ecohydrology, Год журнала: 2025, Номер 18(1)

Опубликована: Янв. 1, 2025

ABSTRACT An experimental study was conducted to investigate the influence of emergent flexible floodplain (FP) vegetation on turbulent flow structure in a symmetric compound channel. The foliage patterns artificial used our sets were as follows: no vegetation, homogeneous grass and shrubs heterogeneous mixture arranged staggered pattern. analysis velocity data revealed an observable decrease across FP owing presence significant increase mean streamwise middle main channel (MC). effect higher case vegetation. This indicates that provides resistance than or separately. It enhances lateral momentum transfer fast‐moving MC low‐velocity flow. kinetic energy (TKE) Reynolds shear stress (RSS) vegetative non‐vegetative In contrast, these lower FP. octant showed ejection events both sweep reduction contributed breakdown vortices reduced turbulence. Meanwhile, enhanced sediment entrainment. These results indicate significantly affects dynamics parameters

Язык: Английский

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Turbulent flow structures and Reynolds stress anisotropy in an asymmetric sinuous mobile channel

Physics of Fluids, Год журнала: 2024, Номер 36(8)

Опубликована: Авг. 1, 2024

In the current experimental study, turbulent flow structures and Reynolds stress anisotropy in an asymmetric sinuous mobile channel are investigated. Experiments were conducted a laboratory on plane-shaped model of riverway with sinuosity 1.23. Three-dimensional instantaneous velocity data measured using acoustic Doppler vectrino profiler processed to compute anisotropy. Spectral analysis streamwise fluctuating component shows presence “−1” “−5/3” slope regions. Analysis bursting events near-bed region reveals that contribution sweep ejection is more dominant than outward inward interactions. The intermixing depth helical flow. probability occurrence indicated ejections higher other events. tensor showed followed by transverse vertical directions, respectively, at all locations. anisotropic invariant map two-component turbulence one-component toward surface upstream apex At bend downstream, diminished near bed, increased depth. eigenvalues non-dimensional principal was two components started decreasing increasing function tended approach isotropic limit but departed from it outer

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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Turbulent dissipation rate and length-scale anisotropy through passive grid turbulence

Physics of Fluids, Год журнала: 2025, Номер 37(3)

Опубликована: Март 1, 2025

This study aims to characterize the range of eddy sizes in grid-generated turbulence within a three-dimensional framework, examining structures arising from interactions between turbulent flow and rigid boundary. The utilizes velocity time-series, processed time-averaged examine both large-scale small-scale characteristics induced by passive grid. integral length scale (in stream-wise, lateral, vertical directions) is calculated using auto-correlation function, while Taylor (also determined gradient approach. approach allows us capture compare dynamics across different mesh configurations. Taylor's length-scale anisotropy are also presented understand directional (eddy sizes) at downstream locations results demonstrate that as grid's size increases, fluctuations stream-wise directions, along with kinetic energy, decrease near boundary regions. significantly increase near-field far-field regions for all three when compared no-grid case. deviations surrogates dissipation rates more pronounced those locally isotropic conditions due increased shear resulting flow. invariant map rate tensor Reynolds stress positions reveals predominantly aligned one direction.

Язык: Английский

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Laboratory investigation on flow structure and turbulent characteristics in low sinuous compound channels with vegetated floodplains

Journal of Hydrology, Год журнала: 2023, Номер 618, С. 129178 - 129178

Опубликована: Фев. 2, 2023

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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Exploring the influence of vegetated mid-channel bar on flow and turbulence in bifurcated channels: An experimental approach

Advances in Water Resources, Год журнала: 2024, Номер 189, С. 104727 - 104727

Опубликована: Май 22, 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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Turbulence characteristics in partially vegetated open channels with alternating sparse and dense patches

Physics of Fluids, Год журнала: 2024, Номер 36(1)

Опубликована: Янв. 1, 2024

A large amount of vegetation in nature exists the form heterogeneous patches, and variations characteristics significantly affect water flow structures. The objective this study is to investigate effect alternating sparse dense patches on turbulence characteristics. Multiple sets scenarios were designed for numerical simulation analysis, a comparison was made with homogeneous vegetation. Results indicate that compared vegetation, arrangement alters distribution velocities zone main channel, promoting material exchange between these regions. density difference channel increases larger differences, but magnitude limited generally remains within 10% width. In balance equation turbulent kinetic energy, terms are influenced differently by changes density. As increases, convective term gradually while production diffusion exhibit “lower middle, higher at both ends” pattern. dissipation demonstrates reduction low-density ultimately exhibits an amplification effect. Furthermore, determines using data from mid-height represent entire cross section may result maximum error up 11%.

Язык: Английский

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