Hydrodynamic characteristics of flow over emergent vegetation in a strongly curved channel

Yang, Yuyi; Lin, Ying-Tien; Ji, Xiaoyan

doi:10.1080/00221686.2021.1944920

Cited by 11 publications

(14 citation statements)

References 52 publications

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“…Inside the vegetation region (Figure 10b), under the coupling effect of vegetation stems and the stratification environment, the typical velocity profile can be seen to be seriously distorted. When vegetation is denser, velocity becomes smaller and more uniform along the vertical direction, as in the case of an open channel flow [26]. After the vegetation region (Figure 10c), the velocity profiles are significantly changed, and the reduced level of velocity is proportional to the density of vegetation patches.…”

Section: Velocity Profilesmentioning

confidence: 91%

Propagation and Separation of Downslope Gravity Currents over Rigid and Emergent Vegetation Patches in Linearly Stratified Environments

Lin

Dongrui

et al. 2022

JMSE

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Large eddy simulation (combined with the mixture model) and laboratory experiment were used to investigate the impact of emergent and rigid vegetation on the dynamics of downslope gravity currents in stratified environments. The reliability of the numerical model was assessed with the corresponding laboratory measurements. The results show that the vegetation cylinders lead to severe lateral non-uniformity of the current front, causing more evident lobe and cleft structures. In stratified environments, the smaller driving force leads to less propagating velocity until the current separates from the slope. The transition point (from acceleration to deceleration phases) of current velocity appears earlier as the vegetation becomes denser. The peak value of the bulk entrainment coefficient Ebuik is inversely proportional to the vegetation density, while the final converged value of Ebuik is proportional to the vegetation density. Vegetation patches make the degree of fluctuation of the instantaneous entrainment coefficient Einst more intense, and even negative values appear locally, indicating that the gravity current is detrained into the ambient fluid. The velocity profiles of gravity current develop multi-peak patterns in stratified environments due to fingering intrusive patterns. Our analysis reveals that as the vegetation density increases, the generated wakes behind vegetation cylinders increase local entrainment and mixing, causing the density of current flow from vegetation to decrease and reach the neutral buoyancy layer of ambient fluids earlier, finally leading to a smaller separation depth.

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Section: Velocity Profilesmentioning

confidence: 91%

Propagation and Separation of Downslope Gravity Currents over Rigid and Emergent Vegetation Patches in Linearly Stratified Environments

Lin

Dongrui

et al. 2022

JMSE

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“…The cylinders in the vegetation region were randomly distributed (see the green‐dotted rectangle in Figure 1) as previous research did (Zhang & Nepf, 2008) to better represent natural vegetation. In addition, up to three or four cylinders were removed near the measurement points to prevent the intrusion of vegetation stems into the sampling volume of the ADVP and affect its accuracy (Ghisalberti and Nepf., 2002; Yang et al., 2021). This process has a negligible impact on the measured velocity statistics (Caroppi et al., 2020).…”

Section: Methodsmentioning

confidence: 99%

“…However, complex vegetation configurations grant an additional supply of turbulent energy. The turbulent kinetic energy (TKE) can be used to quantitatively assess the turbulent intensity (Venuleo et al, 2019;Yang et al, 2021) and is defined as, (Zordan, Juez, et al, 2018;,…”

Section: Turbulent Kinetic Energymentioning

confidence: 99%

“…The sampling volume of the ADVP for turbidity currents was set at approximately 0.12 cm 3 , which meets the accuracy requirements of the experimental data (He et al., 2022). The signal‐to‐noise ratio (SNR) and the correlation level represent the quality of the collected data and were more than 15% and 75%, respectively (Sharma et al., 2017; Yang et al., 2021). The widely used despiking method proposed by Goring and Nikora (2002) was employed to remove and replace noisy data.…”

Section: Experimental Setup and Parametersmentioning

confidence: 99%

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Hydrodynamics and Sediment Transport of Downslope Turbidity Current Through Rigid Vegetation

Han

Lin

et al. 2023

Water Resources Research

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Systematical downslope‐turbidity‐current experiments were performed to clarify the relationship between sediment‐transport modes and current propagation patterns caused by rigid vegetation, as well as adjustments in turbulence characteristics of current. The equations for predicting the front velocities of downslope turbidity currents with emergent vegetation were proposed and validated via experimental data. Experimental results reveal that sediment deposition causes the lower turbulent kinetic energy (TKE) peaks of turbidity currents to decrease or even disappear without affecting their upper TKE peaks, while the rigid vegetation has the opposite effect. Vegetation stems destroy the longitudinal low‐high speed streaks associated with the quasi‐streamwise eddies in the near‐bed region and increase the proportions of the outward and inward interactions. In addition, sediment deposition severely suppresses the turbulent bursting events within turbidity currents but does not influence the relative proportions of the four bursting types. Rigid vegetation and sediment deposition both degrade the absolute values of the third‐order moments of velocity fluctuations without changing their signs to reduce the generation frequency of sweep events. Emergent rigid vegetation accelerates the formation of the reflected bore to provide energy for the deposited sediment to move downstream continuously. On the other hand, the dense submerged vegetation makes turbidity currents easily form the two‐head propagating mode, which allows part of the sediments carried by the upper current head to be transported downstream rather than deposited within or upstream of the vegetation region. Furthermore, the sloping boundary provides favorable conditions to initiate these specific modes for sediment transport adjusted by rigid vegetation.

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“…At present, there are many studies on the mechanical properties and hydraulic properties of soil [1][2][3]. Accurate prediction of permeability coefficient is an important prerequisite for studying soil water conservancy characteristics, and it plays an important role in the impact of groundwater on buildings, slope instability caused by rainfall, seepage and diffusion of pollutants in landfills, and seepage prevention of soil dams.…”

Section: Introductionmentioning

confidence: 99%

Simple Graphical Prediction of Relative Permeability of Unsaturated Soils under Deformations

et al. 2021

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At present, there are only a few existing models that can be used to predict the relative permeability of unsaturated soil under deformations, and the calculation process is relatively complex. In order to fit the measured value of the relative permeability coefficient of unsaturated soil before deformation, this work employs the simplified unified model of the relative permeability coefficient of unsaturated soil, and it obtains the index λ before deformation of the soil. In addition, the value of index λ remains unchanged before and after deformation. Based on the actual measured value of the soil–water characteristic curve before deformation, the air-entry value prediction model is used to predict the air-entry value of soil with different initial void ratios. The relative permeability coefficient of unsaturated soil is then conveniently predicted using the graphical method in combination with the simplified unified model. The method is validated by using the test data of silt loam, sandy loam, and unconsoildated sand. The results show that the predicted results are consistent with the measured values. The prediction method in this paper is simple and overcomes the limitations associated with the determination of the index λ. It expands the application range of the unsaturated relative permeability coefficient model while improving the accuracy of predictions.

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Hydrodynamic characteristics of flow over emergent vegetation in a strongly curved channel

Cited by 11 publications

References 52 publications

Propagation and Separation of Downslope Gravity Currents over Rigid and Emergent Vegetation Patches in Linearly Stratified Environments

Propagation and Separation of Downslope Gravity Currents over Rigid and Emergent Vegetation Patches in Linearly Stratified Environments

Hydrodynamics and Sediment Transport of Downslope Turbidity Current Through Rigid Vegetation

Simple Graphical Prediction of Relative Permeability of Unsaturated Soils under Deformations

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