scholarly journals Global mapper 15.0: A comparative software tool in the design of open channel drainage systems

2021 ◽  
Vol 46 (3) ◽  
pp. 61-73
Author(s):  
Chikwue Maxwell ◽  
Njoku Chumaraoke ◽  
Nwakuba Nnaemeka ◽  
Ezedozie Patrick ◽  
Okorafor Okay
Keyword(s):  
Channel Flow ◽  
Open Channel ◽  
Overland Flow ◽  
Flood Hazard ◽  
Rectangular Channel ◽  
Peak Discharge ◽  
Design Parameters ◽  
Design Capacity ◽  
Watershed Analysis ◽  
The Mean

This research aimed at computing peak flow discharge using state-of-theart technology for watershed analysis to design a suitable open channel to minimize the effects of flood hazard during and after rainfall in an environment. A comprehensive topographical survey data obtained by Shuttle Radar Topographic Mission was employed in this study. The result of the survey shows that both the maximum and minimum elevation at 61.9 m and 51.1 m, respectively, and the mean slope of the area was 0.012. Watershed analysis of the study area was carried out using the Global Mapper15.0. The result shows that the parameters obtained such as the mean area of the sub-catchments is 1.43 ha, the mean length of channel flow is 99.33 m, the mean length of overland flow is 111.81 m, mean upstream elevation for overland flow is 63.30 m, mean downstream elevation for overland flow is 62.37 m and mean downstream elevation for channel flow is 61.12 m. The intensity duration frequency curve of the catchment was developed and a return period of 25 years was used to obtain an average rainfall intensity of 218.81 mm/hr. The peak discharge was obtained as 2.01 m3 /s using rational formula due to the area of the watershed being less than 80 hectares. Finally, several design parameters for the modeled rectangular channel were calculated. The result indicated that the width of the channel is 0.80 m and the depth of the channel is 1.0 m. The developed modeled channel has a design capacity of 2.03 m3 /s which is greater than watershed peak discharge 2.01 m3 /s. The size of the modeled channel was compared with the size of the existing channel and the result revealed that the existing drain was insufficient to carry the discharge from the catchment area due to its design capacity of 0.91m3 /s. It is recommended that the dimension of the existing drain should be increased to meet with the dimension of the modeled drain and a discharge point (safe outlet) should be provided.

scholarly journals Turbulence structure of non-uniform rough open channel flow

2018 ◽  
Vol 40 ◽  
pp. 05039
Author(s):  
Priscilla Williams ◽  
Vesselina Roussinova ◽  
Ram Balachandar
Keyword(s):  
Pressure Gradient ◽  
Channel Flow ◽  
Friction Velocity ◽  
Open Channel ◽  
Open Channel Flow ◽  
Shear Stresses ◽  
Turbulence Structure ◽  
Mean Flow ◽  
Rough Bed ◽  
The Mean

This paper focuses on the turbulence structure in a non-uniform, gradually varied, sub-critical open channel flow (OCF) on a rough bed. The flow field is analysed under accelerating, near-uniform and decelerating conditions. Information for the flow and turbulence parameters was obtained at multiple sections and planes using two different techniques: two-component laser Doppler velocimetry (LDV) and particle image velocimetry (PIV). Different outer region velocity scaling methods were explored for evaluation of the local friction velocity. Analysis of the mean velocity profiles showed that the overlap layer exists for all flow cases. The outer layer of the decelerated velocity profile was strongly affected by the pressure gradient, where a large wake was noted. Due to the prevailing nature of the experimental setup it was found that the time-averaged flow quantities do not attained equilibrium conditions and the flow is spatially heterogeneous. The roughness generally increases the friction velocity and its effect was stronger than the effect of the pressure gradient. It was found that for the decelerated flow section over a rough bed, the mean flow and turbulence intensities were affected throughout the flow depth. The flow features presented in this study can be used to develop a model for simulating flow over a block ramp. The effect of the non-uniformity and roughness on turbulence intensities and Reynolds shear stresses was further investigated.

scholarly journals Diffusion of a Passive Scalar in a Two-dimensional Channel Flow

1973 ◽  
Vol 26 (3) ◽  
pp. 327 ◽  
Author(s):  
MJ Manton
Keyword(s):  
Channel Flow ◽  
Asymptotic Representation ◽  
Open Channel ◽  
Passive Scalar ◽  
Channel Flows ◽  
Two Dimensional ◽  
Open Channel Flows ◽  
The Mean

The asymptotic representation of the distribution of a passive scalar within a two-dimensional channel flow is derived. The distribution is shown to be Gaussian with a skewness and longitudinal variance determined primarily by the mean shear. The distributions corresponding to both laminar and turbulent open channel flows are discussed.

scholarly journals Experimental dataset and numerical simulation of floating bodies transport in open-channel flow

2020 ◽  
Vol 22 (5) ◽  
pp. 1161-1181
Author(s):  
Elisabetta Persi ◽  
Gabriella Petaccia ◽  
Stefano Sibilla ◽  
Pilar Brufau ◽  
José Ignacio García-Palacin
Keyword(s):  
Channel Flow ◽  
Water Surface ◽  
Open Channel ◽  
Numerical Models ◽  
Rectangular Channel ◽  
Open Channel Flow ◽  
Body Motion ◽  
Lagrangian Model ◽  
Floating Body ◽  
Floating Bodies

Abstract Numerical models trying to faithfully represent the movement of floating bodies transport in open-channel flow require experimental data for validation. In order to provide an adequate dataset, flume experiments were carried out to analyse the transport of singular and grouped rigid bodies floating on the water surface. Both cylindrical and spherical samples were employed: they were released in a rectangular channel under steady conditions in one-dimensional (plain channel) and two-dimensional (2D) configurations using one rectangular side obstacle, one smooth side obstacle or two rectangular alternate obstacles. The outcomes of the experiments are the planar displacement and the rotation of the samples, which are related to the flow field in the different configurations. The detailed experimental analysis of the floating body motion provides information for the calibration of numerical models simulating floating bodies transport. This dataset is thus employed for the validation of the Eulerian–Lagrangian model ORSA2D_WT, highlighting its strengths and improvable aspects. Similar applications could be carried out with any 2D model which performs the simulation of discrete elements moving on the water surface.

scholarly journals Experimental Investigation of Turbulence Diffusion—A Factor in Transportation of Sediment in Open-Channel Flow

1945 ◽  
Vol 12 (2) ◽  
pp. A91-A100
Author(s):  
E. R. Van Driest
Keyword(s):  
Experimental Investigation ◽  
Channel Flow ◽  
Open Channel ◽  
Open Channel Flow ◽  
The Other ◽  
Immiscible Fluid ◽  
Mean Square ◽  
Velocity Correlation ◽  
Correlation Curve ◽  
The Mean

Abstract Turbulence diffusion in open-channel flow was investigated experimentally by photographing the spread of globules formed by the injection of an immiscible fluid into water. The mean-square transverse deviations of the globules at various distances downstream from the source were computed and analyzed in an effort to determine the shape of the velocity-correlation curve. Comparison was made between two types of curve which fitted the deviation data, one corresponding to a power-correlation law and the other to an exponential-correlation law.

PIV Study of Separated and Reattached Open Channel Flow Over Surface Mounted Blocks

2008 ◽  
Vol 130 (6) ◽  
Author(s):  
Martin Agelinchaab ◽  
Mark F. Tachie
Keyword(s):  
Boundary Layer ◽  
Shear Layer ◽  
Channel Flow ◽  
Open Channel ◽  
Open Channel Flow ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Mean Velocity ◽  
High Background ◽  
The Mean

A particle image velocimetry is used to study the mean and turbulent fields of separated and redeveloping flow over square, rectangular, and semicircular blocks fixed to the bottom wall of an open channel. The open channel flow is characterized by high background turbulence level, and the ratio of the upstream boundary layer thickness to block height is considerably higher than in prior experiments. The variation of the Reynolds stresses along the dividing streamlines is discussed within the context of vortex stretching, longitudinal strain rate, and wall damping. It appears that wall damping is a more dominant mechanism in the vicinity of reattachment. In the recirculation and reattachment regions, profiles of the mean velocity, turbulent quantities, and transport terms are used to document the salient features of block geometry on the flow. The flow characteristics in these regions strongly depend on block geometry. Downstream of reattachment, a new shear layer is formed, and the redevelopment of the shear layer toward the upstream open channel boundary layer is studied using the boundary layer parameters and Reynolds stresses. The results show that the mean flow rapidly redeveloped so that the Clauser parameter recovered to its upstream value at 90 step heights downstream of reattachment. However, the rate of development close to reattachment strongly depends on block geometry.

Experimental Study of Shallow Open Channel Turbulent Flows Over Rough Walls

2014 ◽  
Author(s):  
B. Nyantekyi-Kwakye ◽  
E. E. Essel ◽  
S. Clark ◽  
M. F. Tachie
Keyword(s):  
Boundary Layer ◽  
Experimental Study ◽  
Reynolds Number ◽  
Channel Flow ◽  
Open Channel ◽  
Open Channel Flow ◽  
Reynolds Stresses ◽  
Freestream Velocity ◽  
The Mean ◽  
Bed Roughness

An experimental study was undertaken to investigate the effects of bed roughness on the turbulence characteristics of shallow open channel flows. The measurements were performed in a recirculating open channel flow over a reference smooth bed and a three-dimensional rough bed (36-grit sandpaper). The velocity measurements were conducted using a high resolution particle image velocimetry (PIV) system. The Reynolds number based on the depth of flow (h) and freestream velocity (Ue) varied from 21000 to 30000 and the Froude number ranged from 0.46 to 0.65. Two smooth bed experiments were conducted to investigate the effect of Reynolds number on the open channel flow. The mean velocities and Reynolds stresses for the two smooth cases were observed to be weakly dependent on Reynolds number. The effect of bed roughness was observed to penetrate into the outer layer of the boundary layer. The results show that bed roughness significantly increased the skin friction coefficient, wake parameter, boundary layer parameters, as well as the mean velocity, Reynolds stresses and the energy budget terms. A two-point correlation analysis showed that the coherent structures were also significantly modified by bed roughness.

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