scholarly journals Study on the influence of ecological vegetation revetment on river flow and sediment environment

2020 ◽  
Vol 20 (8) ◽  
pp. 3141-3155
Author(s):  
Yanhua Yang ◽  
Shuqing Yang ◽  
Xin Wang ◽  
Chenyang Wang ◽  
Jianjun Wang
Keyword(s):  
Flow Velocity ◽  
Suspended Sediment ◽  
Water Flow ◽  
Turbulence Intensity ◽  
Fixed Bed ◽  
Suspended Load ◽  
Flow Environment ◽  
Load Movement ◽  
Movable Bed ◽  
Submerged Conditions

Abstract This paper studied the influence of vegetation cover on the river water flow environment and on sediment suspended load movement environment, closely combining the development and construction of new ecological water conservancy projects such as ecological embankments and ecological wetlands with ecological vegetation revetment cultivated on river bank slopes. The glass flume experiment was carried out in the vegetation-water flow-sediment environment. In the experiment, natural straight holly in the early growth stage was selected as the experimental vegetation, and erect type vegetation with uniform distribution of the upper and lower branches and leaves was simulated, and a total of 14 experimental groups were set in different combinations with fixed bed, movable bed, submerged and non-submerged conditions. The measured data of flow quantity, flow velocity and suspended load concentration were achieved in the experiment. The experimental results show that: (1) as to the influence of vegetation on the water flow environment, the vegetation canopy density directly affects the turbulent environment of the water flow, and the greater the density, the greater the disturbance to the water flow environment, and the flow velocity near the canopy will be decreased sharply; (2) in the fixed bed, under submerged conditions, the maximum turbulence intensity appears near z/h = 0.6; under non-submerged conditions, the turbulence intensity near the water surface is largest. In the movable bed, under submerged conditions, the maximum turbulence intensity reaches the maximum in the top and upper locations of the top of the plant, and the turbulence intensity reaches the maximum at the top of the plant under non-submerged conditions. (3) In terms of the influence of vegetation on the sediment suspended load movement environment, the concentration of suspended sediment decreases with the increase of plant height, the sediment content in the tail of the plant belt is reduced to some degree. When the relative water depth is z/h > 0.5, almost no suspended sediment exists. And the sediment-retaining effect under non-submerged conditions is better than that under submerged conditions.

scholarly journals Vertical Distribution of Suspended Sediments above Dense Plants in Water Flow

Water ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 12 ◽  
Author(s):  
Yanhong Li ◽  
Liquan Xie ◽  
Tsung-chow Su
Keyword(s):  
Vertical Distribution ◽  
Flow Velocity ◽  
Suspended Sediment ◽  
Plant Height ◽  
Water Flow ◽  
Suspended Sediments ◽  
Sediment Concentration ◽  
Turbulent Momentum ◽  
Different Diameters ◽  
Plane Displacement

Plants in natural water flow can improve water quality by adhering and absorbing the fine suspended sediments. Dense plants usually form an additional permeable bottom boundary for the water flow over it. In the flow layer above dense plants, the flow velocity generally presents a zero-plane-displacement and roughness-height double modified semi-logarithmic profile. In addition, the second order shear turbulent moment (or the Reynolds stress) are different from that found in non-vegetated flow. As a result, the turbulent momentum diffusivity of flow and thus the diffusivity of sediment will shift, which will cause the vertical profile of suspended sediment and the corresponding Rouse formula deform. A set of physical experiments with three different diameters of fine suspended sediments was conducted in an indoor water flume. These experiments investigated a new distribution pattern of suspended sediment and the correspondingly deformed Rouse formula in the flow layer over the dense plants. Experimental results showed that above the dense plants, the shear turbulent momentum of flow presented a plant-height modified negative linear profile, which has been proposed by a previous study, and the vertical distribution of fine suspended sediments presented an equilibrium pattern. Based on the plant-modified profiles of flow velocity and the shear turbulent momentum a new zero-plane and plant-height double modified Rouse formula were analytically derived. This double-parameter modified Rouse formula agrees well with the measured profile of suspended sediment concentration experimentally observed in the present study. By adjusting the Prandtl–Schmidt number, i.e., the ratio of sediment diffusivity to flow diffusivity, the double-parameter modified Rouse formula can be applied to submerged dense plant occupied flow.

scholarly journals Effect of a Lateral Jet on the Turbulent Flow Characteristics of an Open Channel Flow with Rigid Vegetation

Water ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 1204 ◽  
Author(s):  
Sufen Teng ◽  
Minquan Feng ◽  
Kailin Chen ◽  
Weijie Wang ◽  
Bangmin Zheng
Keyword(s):  
Flow Velocity ◽  
Reynolds Stress ◽  
Water Flow ◽  
Channel Flow ◽  
Turbulence Intensity ◽  
Open Channel ◽  
Aquatic Vegetation ◽  
Open Channel Flow ◽  
Rigid Vegetation ◽  
Bodies Of Water

Aquatic vegetation can purify polluted bodies of water and beautify the environment, as well as alter the structure of water flow and affect the migration and diffusion of pollutants in bodies of water. Vegetation can significantly change the original water flow, especially in cases in which aquatic vegetation interacts with a jet. Characteristics of jet flow open channels without vegetation have been studied, but research on the characteristics of open-channel flows under the action of lateral jets and in the presence of vegetation are rare. High-frequency particle image velocimetry (PIV) was used to measure a lateral jet in water with rigid vegetation and our results were compared to the lateral jet flow field in water without vegetation. The results show that the vegetation arrangement and vegetation resistance cause significant changes. The presence of vegetation increased the surface velocity of the water, and the flow velocity decreased in the interior area of the vegetation and near the bottom of the water tank. The changes in flow velocity with changes in water depth displayed “S” type and anti-“S” type distributions, and the flow velocity of free layer was approximately logarithmic. Due to vegetation resistance and jet pressure differences, the lateral jet trajectory in water with vegetation was more likely to bend than in water without vegetation. The turbulence intensity and Reynolds stress had different distributions for water with and without vegetation. At the top of the vegetation and near the water surface, turbulent mixing of the water flow was strong, the flow velocity gradient was large and the turbulence intensity and the Reynolds stress reached their maxima. The effects of a lateral jet on an open-channel flow were compared for different vegetation conditions, revealing that a rhombic vegetation arrangement has a stronger deceleration effect than other arrangements. The theoretical results can be applied to wastewater discharge into vegetation channels.

Investigation of the influence of the flow structure on the accuracy of flow measurement before a hydrometric structure in an open channel

2020 ◽  
pp. 41-44
Author(s):  
Anatoly Kusher
Keyword(s):  
Velocity Profile ◽  
Flow Velocity ◽  
Water Flow ◽  
Flow Measurement ◽  
Water Discharge ◽  
Critical Depth ◽  
Flow Measurements ◽  
Study Results ◽  
Flow Velocity Profile ◽  
Upstream Flow

The reliability of water flow measurement in irrigational canals depends on the measurement method and design features of the flow-measuring structure and the upstream flow velocity profile. The flow velocity profile is a function of the channel geometry and wall roughness. The article presents the study results of the influence of the upstream flow velocity profile on the discharge measurement accuracy. For this, the physical and numerical modeling of two structures was carried out: a critical depth flume and a hydrometric overfall in a rectangular channel. According to the data of numerical simulation of the critical depth flume with a uniform and parabolic (1/7) velocity profile in the upstream channel, the values of water discharge differ very little from the experimental values in the laboratory model with a similar geometry (δ < 2 %). In contrast to the critical depth flume, a change in the velocity profile only due to an increase in the height of the bottom roughness by 3 mm causes a decrease of the overfall discharge coefficient by 4…5 %. According to the results of the numerical and physical modeling, it was found that an increase of backwater by hydrometric structure reduces the influence of the upstream flow velocity profile and increases the reliability of water flow measurements.

The effects of changing water flow velocity on the formation of biofilms and water quality in pilot distribution system consisting of copper or polyethylene pipes

2006 ◽  
Vol 40 (11) ◽  
pp. 2151-2160 ◽  
Author(s):  
Markku J. Lehtola ◽  
Michaela Laxander ◽  
Ilkka T. Miettinen ◽  
Arja Hirvonen ◽  
Terttu Vartiainen ◽  
...  
Keyword(s):  
Water Quality ◽  
Flow Velocity ◽  
Water Flow ◽  
Distribution System ◽  
Water Flow Velocity ◽  
Polyethylene Pipes

scholarly journals A NEW FULLY-AUTOMATIC PROCEDURE FOR THE IDENTIFICATION AND THE COUPLING OF THE OVERTOPPING WAVES

2018 ◽  
pp. 36 ◽  
Author(s):  
Sara Mizar Formentin ◽  
Barbara Zanuttigh
Keyword(s):  
Flow Velocity ◽  
Water Surface ◽  
Automatic Identification ◽  
Practical Relevance ◽  
Threshold Values ◽  
Flow Conditions ◽  
Fully Automatic ◽  
The Individual ◽  
Coupling Algorithm ◽  
Submerged Conditions

This contribution presents a new procedure for the automatic identification of the individual overtopping events. The procedure is based on a zero-down-crossing analysis of the water-surface-elevation signals and, based on two threshold values, can be applied to any structure crest level, i.e. to emerged, zero-freeboard, over-washed and submerged conditions. The results of the procedure are characterized by a level of accuracy comparable to the human-supervised analysis of the wave signals. The procedure includes a second algorithm for the coupling of the overtopping events registered at two consecutive gauges. This coupling algorithm offers a series of original applications of practical relevance, a.o. the possibility to estimate the wave celerities, i.e. the velocities of propagation of the single waves, which could be used as an approximation of the flow velocity in shallow water and broken flow conditions.

scholarly journals Suspended Sediment Analysis: Case Study of Berounka Sources

Geografie ◽  
1997 ◽  
Vol 102 (2) ◽  
pp. 130-138
Author(s):  
Zdeněk Kliment ◽  
Jan Kopp
Keyword(s):  
Seasonal Variation ◽  
Sediment Transport ◽  
Suspended Sediment ◽  
Inorganic Material ◽  
Suspended Sediments ◽  
Suspended Load ◽  
Suspended Sediment Transport ◽  
Sediment Analysis ◽  
Load Characteristics

The article examines suspended sediment transport in Mže, Radbuza, and Úhlava Rivers over the period 1989-95. Data on suspended sediments was collected at five observing sites. The research has been carried out in collaboration with Czech Hydrometeorological Institute, Plzeň. Apart from the suspended load characteristics also the seasonal variation of suspended sediments, siltation of Hracholusky and České Údolí Lakes, and the share of inorganic material in suspended sediments have been examined.

scholarly journals Measuring thermal conductivity of soils under laboratory conditions.

1969 ◽  
Vol 17 (1) ◽  
pp. 71-79
Author(s):  
A.I. Golovanov
Keyword(s):  
Thermal Conductivity ◽  
Flow Velocity ◽  
Soil Sample ◽  
Water Flow ◽  
Coarse Sand ◽  
Conductivity Measurements ◽  
Soil Layers ◽  
The Real ◽  
Real Flow

Experiments were made to determine the influence of size of soil sample, convection and water flow on the determination of thermal conductivity of soils using a thin needle (0.05 cm radius, 8.5 cm in length) as the heating element and copper cylinders for sample containers. For measurements during a period of 100 seconds the diameter of the sample must be at least 4 cm and to avoid any influence of convection measurements should not exceed 100 seconds. When heating elements are placed horizontally to measure simultaneously the thermal conductivity of different soil layers they should be placed at least 10 cm apart. Thermal conductivity measurements could be used to determine flow velocities of water in coarse sand samples provided that the real flow velocity was highev than 0.35 cm/ min. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Effect of slope gradient on the subsurface water flow velocity of sand layer profile

2020 ◽  
Vol 17 (3) ◽  
pp. 641-652 ◽  
Author(s):  
Zhen Han ◽  
Xiao-yan Chen ◽  
Yu-han Huang ◽  
Bang-lin Luo ◽  
Hang Xing ◽  
...  
Keyword(s):  
Flow Velocity ◽  
Water Flow ◽  
Subsurface Water ◽  
Sand Layer ◽  
Slope Gradient ◽  
Water Flow Velocity

Effect of Blockage Size on Pipe Vibration

2012 ◽  
Vol 626 ◽  
pp. 993-996
Author(s):  
N. Liyana Tajul Lile ◽  
M.J. Hasnul ◽  
R.A. Siregar ◽  
J.C. Leong
Keyword(s):  
Flow Velocity ◽  
Turbulence Intensity ◽  
Vibration Analysis ◽  
Vibration Response ◽  
Circular Pipe ◽  
Flow Area ◽  
Circular Pipes ◽  
External Objects ◽  
Vibration Parameters ◽  
Pipe Vibration

Circular pipes are widely used to convey goods to a desired location. Flow inside a pipe needs to be smoothed and unobstructed to ensure an optimize flow of particle. However, pipes are prone to clogging or blocking due to deposition of unwanted impurities and external objects. Built up inside a circular pipe will affect the flow velocity and pressure within the pipe. This paper presents a method of assessing blockage inside a pipe by using vibration analysis. The effect of blockage was observed through changes in pipe vibration response and also turbulence intensity. The changes in vibration parameters were identified together with the reduction of flow area due to increasing blockage size.

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