Flow velocity evolution through a floating rigid cylinder array under unidirectional flow

Vertically discharged multiple jets in crossflow is a common form of wastewater discharge. The presence of vegetation in the flow channel complicates the hydraulic characteristics of jets. The realizable k-ε turbulent model is used to simulate the flow, turbulence, and vortex characteristics of multiple jets with different spacing and jet-to-crossflow velocity ratios, to study the flow characteristics and vortex structure of multiple jets in a vegetated channel. The results reveal that vegetation inhibits the development of a counterrotating vortex pair. The jets with a low jet-to-crossflow velocity ratio are concentrated near the flow symmetry profile by the dual constraints of ambient flow and vegetation. The jets gradually spread outward and the counterrotating vortex pair become more obvious when the jet-to-crossflow velocity ratio increases. Vegetation reduces the shading effect of the front jet on the rear jet by accelerating the dissipation of shear layer vortices. The influence of the front jet on the rear jet decreases as the spacing increases.

Section: Mean Velocity Fieldmentioning

confidence: 99%

Numerical Study of Multiple Momentum Jets in a Vegetated Crossflow

Yuan,

Xia,

Zhao

et al. 2023

“…Pontederia crassipes is a widespread hydrophyte and has developed a root system for the uptake of nutrients and pollutants [8,9]. Pontederia crassipes can tolerate strong acid and alkaline environments, and rapidly grows in wastewater, where it can accumulate heavy metals [10,11].…”

Section: Introductionmentioning

confidence: 99%

Effect and Mechanism of Bicarbonate Ion on Lead Absorption in Pontederia crassipes from Karst Water

Zhou,

Jiang,

Qin

et al. 2024

Bicarbonate ions (HCO3−) are abundant in karst water with poor lead (Pb) utilization and biodegradation. This study aimed to investigate the mechanism of HCO3− on the Pb removal efficiency and uptake ability of Pontederia crassipes (a widespread hydrophyte in the karst area) from karst water. The Pb concentration, Pontederia crassipes morphology, and functional group were detected. As the HCO3− molarity in karst water increased (3, 4, and 5 mmol/L), the removal of Pb increased (85.31%, 93.28%, and 95.16%), whereas the bioconcentration amount of Pb decreased (573, 501, and 301 mg/kg), mainly due to the insoluble PbCO3 and Pb (OH)2. The Pb bioconcentration factor was the highest (15,564) at 4 mmol/L HCO3− due to the maximum strength of cation exchange and cell wall protein C=O. High HCO3− molarities changed the variety of positive ions of cation exchange (HCO3− ≤ 4 mmol/L: Na, K, and Mg; HCO3− > 4 mmol/L: Mg and K), and relieved the breaking of roots, stomatal closure, and vascular system shrinking. Moreover, high HCO3− molarities diminished the C≡C oxidation, enlarged the displacement of SO42− and C-O, and stimulated the methyl transfer reaction and the bonding between -CH3 and Pb.

“…Originally proposed by Leopold and Wolman [2], braided rivers have distinctive geomorphological features, including scattered and fragmented planforms, easily eroded and deposited sandbars, and channels that are constantly branching and reconfiguring, while the complex movement of water and sediment within these rivers makes their geomorphological units highly dynamic [3,4]. These characteristics make it impossible to predict the evolution of flow velocity and sediment deposition in braided rivers by constructing analytical models, as is the case for straight or meandering rivers [5][6][7][8], and therefore, it is difficult to predict the evolution of braided rivers from the point of view of flow structure. The bed structure of braided rivers is complex and variable due to a variety of factors such as different flow and sediment conditions, particle morphology, grain size gradation, and spatial distribution.…”

Section: Introductionmentioning

confidence: 99%

Statistical Roughness Properties of the Bed Surface in Braided Rivers

Ren

Pan

Lin

et al. 2023

Braided rivers are widespread in nature, and their bed morphology is complex and variable. This paper aims to investigate and quantitatively analyze the bed surface roughness of braided rivers utilizing statistical theory. In this paper, a physical model of braided rivers is developed, and four constant discharge experiments are carried out. Based on Structure-from-Motion photogrammetry and direct measurement of bedload transport using a load cell, data on bedload transport rate, bed morphology, and bed elevation are obtained, facilitating the in-depth investigation of the correlations between these parameters. The results show that the morphological active width increases with increasing discharge. There was a significant positive correlation between the morphological active width and the bedload transport rate, although there is considerable scatter due to the inherent variability in braided river morphodynamics. The elevation probability distribution of bed surfaces shows negative skewness and leptokurtic distribution. There is a relatively significant correlation between skewness and the dimensionless bedload transport rate. The two-dimensional variogram values of bed elevation are variable, and the bed is anisotropic. Additionally, both the longitudinal sill and correlation length values exhibit an increase with the rise in stream power. Remarkably, the correlation between the dimensionless sill and correlation length, as well as the dimensionless bedload transport rate, proves to be highly significant. Consequently, this correlation can serve as a reliable general factor for predicting bedload transport rate in the reach.