Longitudinal dispersive coefficient in channels with aquatic vegetation: A review

Journal of Hydrodynamics, Год журнала: 2023, Номер 35(3), С. 379 - 395

Опубликована: Июнь 1, 2023

Язык: Английский

---

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

---

Evolution of coherent structures in the flow around a circular pier with a developing scour hole: A numerical study

Physics of Fluids, Год журнала: 2024, Номер 36(2)

Опубликована: Фев. 1, 2024

Large-eddy simulations (LES) were used to simulate the flow features around a circular pier with evolving scour hole. The bathymetry corresponding four stages of hole evolution, published in previous literature, was domain recreate at particular stage development. growth coherent structures and their interactions developing investigated. formation secondary vortices inside primary horseshoe vortex (HV) made HV system highly dynamic. High-level pressure fluctuations observed core HV. simulation captured bimodal aperiodic oscillations all mechanisms responsible for behind discussed. High levels mean instantaneous bed shear stress values beneath vortex. These found have decreased an increase depth. LES also detachment from legs convection downstream.

Язык: Английский

---

Analysis of the correlation between vegetated flow and suspended sediment using the drift flux model

Physics of Fluids, Год журнала: 2024, Номер 36(4)

Опубликована: Апрель 1, 2024

We propose a model that integrates drift flux with vegetation source term and the k−ω shear stress transport improved delayed detached eddy simulation turbulence to simulate sediment-laden vegetated flows. The numerical was validated using experimental data from Lu [“Experimental study on suspended sediment distribution in flow rigid vegetation,” Ph.D. thesis (Hohai University, Nanjing, Jiangsu, China, 2008)] Wang Qian [“Velocity profiles of flow,” Int. J. Sediment Res. 7, 27–58 (1992)]. analyzed vertical profile characteristics spatial features flows at different densities. A detailed analysis conducted correlations between variables could affect distribution, including vorticity, velocity, Reynolds stress, turbulent kinetic energy (TKE) fields. It found vorticity field is primarily correlated concentration (SSC) canopy, while velocity above canopy has positive correlation SSC field. Both TKE fields exhibit However, below both show negative concentration. closely related near bottom, whereas influences surface. overall negative, their significantly higher than indicating closer connection movement sediments other variables.

Язык: Английский

---

Modeling transverse momentum exchange in partially vegetated flow

Physics of Fluids, Год журнала: 2022, Номер 34(2)

Опубликована: Фев. 1, 2022

In this study, theoretical and experimental methods are applied to investigate streamwise velocity profiles transverse momentum exchange in the quasi-equilibrium region partially vegetated channels. A new eddy viscosity model is proposed consideration of bottom turbulence, stem-scale turbulence induced by coherent structures. Results show that structures dominant contributor exchange. The can be well for different setups varying only one proportionality constant (ξ), which inversely proportional canopy drag (CDa). lateral distribution also predicted shows a peak just outside canopy. By assuming as rough wall setting zero-plane displacement within distance penetration width, we find mean outer shear layer follow logarithmic curves. quantitative relationship between roughness length (CDa) is, thus, determined similar turbulent rough-wall boundary layers.

Язык: Английский

---

Low-Reynolds-number wake of three tandem elliptic cylinders

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

Опубликована: Апрель 1, 2022

The flow around three elliptic cylinders with equal spacing and aspect ratio in tandem arrangements was numerically investigated through direct numerical simulation. (L/D, where D L are the major axis center-to-center distance of two adjacent cylinders, respectively) ranging from 1.5 to 10 Reynolds numbers Re=65−160 (based on D) examined. analysis aims at effects L/D Re wake structures, hydrodynamic forces, Strouhal correlates them underlying physics. is highly changeable L/D, classifying into five distinct regimes, namely, meandering, overshoot, reattachment, quasi-coshedding, coshedding. Two vortex shedding frequencies for middle downstream observed latter indicating significant interference, modes spatially including primary, two-layered, secondary. transition between forms boundaries. At first boundary, vortices divert cylinder centerline follow layers, while converge second boundary. boundary location not stationary Re=65–100, it = 160. Otherwise, moves upstream an increase range movement decreases Re. advances disturbance level urges modes. time-mean lift drag coefficients sensitive L/D.

Язык: Английский

---

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

---

Extraction of flow features around a bridge pier with an evolving scour hole using Lagrangian coherent structures

Physics of Fluids, Год журнала: 2024, Номер 36(5)

Опубликована: Май 1, 2024

Local scouring around a bridge pier poses severe threat to the safety of bridge. A better understanding flow features piers is necessary for accurate prediction scour depth. The ridges finite-time Lyapunov exponent, called Lagrangian coherent structures (LCSs), were used extract circular with an evolving hole. velocity field required LCSs computation was obtained using three-dimensional Reynolds-averaged Navier–Stokes simulation. simulation results validated published experimental and numerical findings. computed LCS stretching extracted all that previously reported in literature. In addition, region acceleration on both sides pier. forward upstream particle trapping region, providing insight into volume fluid converting downflow. They anchor-like inside hole analysis variations along width depth domain revealed change profile triggering formation LCS. behavior non-inertial particles released integrated significance transport. Using method, study difficult traditional visualization methods.

Язык: Английский

---

Reynolds number effect on the parameters of turbulent flows over open channels

AQUA - Water Infrastructure Ecosystems and Society, Год журнала: 2024, Номер 73(5), С. 1030 - 1047

Опубликована: Апрель 16, 2024

ABSTRACT Experimental investigations were conducted to analyze the effect of Reynolds numbers on turbulent flow properties in a nonuniform sand bed channel. Steady simulations performed over channel, considering five within range 36500–53886. This article endeavors delineate influence number through meticulous laboratory studies. Observations revealed that higher corresponded increased longitudinal velocity. As increases by 10 47%, various exhibit distinct trends. Specifically, velocity, intensity, vertical kinetic energy, shear stress, and Taylor scale show ranging from 5 30%, 15 25%, 20%, 25 60%, 20 40%, 35 45%, respectively. analysis indicated magnitudes associated with numbers. In-depth examinations anisotropy, third-order moments velocity fluctuations, kurtosis, energy production, dissipation provided additional insights into behavior across different study contributes more comprehensive understanding dynamics channels under varying conditions, bridging gap between studies real-world scenarios.

Язык: Английский

---

Flow dynamics in lateral vegetation cavities constructed by an array of emergent vegetation patches along the open-channel bank

Physics of Fluids, Год журнала: 2022, Номер 34(3)

Опубликована: Март 1, 2022

The hydrodynamics in a straight rectangular open channel containing novel lateral cavities constructed by an array of square emergent vegetation patches discontinuously distributed along the bank were explored numerically using three-dimensional large eddy simulations (LES). Five densities (Φ), ranging from 0.02 to 0.25, as well traditional created impermeable solid media, tested. effects cavity aspect ratio (AR) also examined. LES results showed that mean recirculation pattern inside and coherent structures horizontal shear layer closely dependent on Φ AR. When ≥ 0.06, main vortex formed resembled within media cavities, whereas extent former increased upstream increased. Compared with cases, exhibited higher turbulent intensity wider regions enhanced kinetic energy, which decreased increasing Φ. penetration depth elevated energy into Φ, deeper was expected at larger AR values. interfacial turbulence dominated “cavities field”-scale vortices ≤ “cavity element”-scale 0.15. = 0.1, both scales contributed enhancement turbulence. mass exchange non-monotonic relationship reached maximum values 1. total momentum transport efficiency monotonically Despite values, motions over most length.

Язык: Английский

---