scholarly journals A Study on the Friction Factor and Reynolds Number Relationship for Flow in Smooth and Rough Channels

Water ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 1714
Author(s):  
Yeon-Moon Choo ◽  
Jong-Gu Kim ◽  
Sang-Ho Park
Keyword(s):  
Friction Coefficient ◽  
Channel Flow ◽  
Open Channel ◽  
Flow Characteristics ◽  
Open Channel Flow ◽  
Shear Velocity ◽  
Estimation Methods ◽  
Flow Conditions ◽  
Key Factors ◽  
Mean Velocity

The shear velocity and friction coefficient for representing the resistance of flow are key factors to determine the flow characteristics of the open-channel flow. Various studies have been conducted in the open-channel flow, but many controversies remain over the form of equation and estimation methods. This is because the equations developed based on theory have not fully interpreted the friction characteristics in an open-channel flow. In this paper, a friction coefficient equation is proposed by using the entropy concept. The proposed equation is determined under the rectangular, the trapezoid, the parabolic round-bottomed triangle, and the parabolic-bottomed triangle open-channel flow conditions. To evaluate the proposed equation, the estimated results are compared with measured data in both the smooth and rough flow conditions. The evaluation results showed that R (correlation coefficient) is found to be above 0.96 in most cases, and the discrepancy ratio analysis results are very close to zero. The advantage of the developed equation is that the energy slope terms are not included, because the determination of the exact value is the most difficult in the open-channel flow. The developed equation uses only the mean velocity and entropy M to estimate the friction loss coefficient, which can be used for maximizing the design efficiency.

Transverse Distribution of the Streamwise Velocity for the Open-channel Flow With Floating Vegetated Islands

2021 ◽  
Author(s):  
Xuecheng Fu ◽  
Feifei Wang ◽  
Mengyang Liu ◽  
Wenxin Huai
Keyword(s):  
Channel Flow ◽  
Open Channel ◽  
Flow Characteristics ◽  
Open Channel Flow ◽  
Streamwise Velocity ◽  
Transport Efficiency ◽  
Transverse Distribution ◽  
Floating Vegetation ◽  
Shear Turbulence ◽  
Field Disturbance

Abstract Floating vegetation islands (FVIs) have been widely utilized in various river ecological restoration projects due to their ability to purify pollutants. FVIs float at the surface of shallow pools with their roots unanchored in the sediment. Biofilm formed by roots under islands filters nutrients and particles in the water flowing through it. Flow field disturbance will occur and transverse distribution of flow velocity will change due to the existence of FVIs. Transport efficiency of suspended solids, nutrients, and pollutants will also be altered. A modified analytical model that considers effects of boundary friction, drag force of vegetation, transverse shear turbulence, and secondary flow is established to predict transverse variation of depth-averaged streamwise velocity for the open-channel flow with FVIs using Shiono and Knight method. The simulation results with suitable boundary conditions successfully predicted lateral profile of the depth-averaged streamwise velocity compared with the experimental results of symmetrical and unsymmetrical arrangements of FVIs. Hence, the presented model can provide guidance for investigating flow characteristics of rivers with FVIs.

scholarly journals Free-surface flows with near-critical flow conditions

1996 ◽  
Vol 23 (6) ◽  
pp. 1272-1284 ◽  
Author(s):  
H. Chanson
Keyword(s):  
Free Surface ◽  
Channel Flow ◽  
Open Channel ◽  
Flow Instability ◽  
Open Channel Flow ◽  
Surface Characteristics ◽  
Free Surface Flows ◽  
Critical Flow ◽  
Flow Conditions ◽  
Weir Flow

Open channel flow situations with near-critical flow conditions are often characterized by the development of free-surface instabilities (i.e., undulations). The paper develops a review of several near-critical flow situations. Experimental results are compared with ideal-fluid flow calculations. The analysis is completed by a series of new experiments. The results indicate that, for Froude numbers slightly above unity, the free-surface characteristics are very similar. However, with increasing Froude numbers, distinctive flow patterns develop. Key words: open channel flow, critical flow conditions, free-surface undulations, flow instability, undular surge, undular broad-crested weir flow, culvert flow.

An experimental investigation of microplastic transport in fluvial systems

2020 ◽  
Author(s):  
Jan-Pascal Boos ◽  
Benjamin-Silas Gilfedder ◽  
Hassan Elagami ◽  
Sven Frei
Keyword(s):  
Porous Media ◽  
Channel Flow ◽  
Open Channel ◽  
Treatment Plant ◽  
Open Channel Flow ◽  
Agricultural Runoff ◽  
Hydrodynamic Flow ◽  
Waste Water Treatment Plant ◽  
Flow Conditions ◽  
Fluvial Systems

<p>Although a major part of marine microplastic (MP) pollution originates from rivers and streams, the mechanistic behavior of MP in fluvial systems is only poorly understood. MP enter fluvial systems from e.g. waste water treatment plant (WWTP) effluents, sewer overflows during heavy rain events, agricultural runoff, aerial input/atmospheric fallout, road runoff or via fragmentation of plastic litter. As part of this project we want to investigate the hydrodynamic transport mechanisms that control the behavior and re-distribution of MP in open channel flow and the streambed sediments. Hydrodynamic conditions in open channel flow are represented in an experimental flume environment.  Different porous media materials (e.g. aqua beads, glass beads and sand) are used in the flume experiments to shape typical bed form structures such as riffle-pool sequences, ripples and dunes. The aim of this experimental setup is to create hydrodynamic flow conditions such as hydraulic jumps, low and high flow velocity environments for which the transport and sedimentation behavior of MP can be investigated under realistic conditions. Hydrodynamic flow conditions in the flume are characterized using a Laser-Doppler-Anemometry (LDA) and Particle Image Velocimetry (PIV). Detection and tracking of fluorescent MP-particles in open channel flow and in porous media will be achieved with a fluorescence-camera-system.</p>

The wall shear velocity, u*, in fixed and eroded beds of 180°-curved open channel flow

2014 ◽  
pp. 1089-1096
Author(s):  
B Kironoto ◽  
B Yulistiyanto ◽  
D Legono ◽  
P Sangging
Keyword(s):  
Channel Flow ◽  
Open Channel ◽  
Open Channel Flow ◽  
Shear Velocity ◽  
Wall Shear

scholarly journals Flow Characteristics in a Gradually Expanded Rectangular Open Channel Flow

1992 ◽  
Vol 36 ◽  
pp. 379-384
Author(s):  
Masaru URA ◽  
Juichiro AKIYAMA ◽  
Junichiro KAWASAKI ◽  
Kouki ONITSUKA
Keyword(s):  
Channel Flow ◽  
Open Channel ◽  
Flow Characteristics ◽  
Open Channel Flow

Low Reynolds Number Effect on Open Channel Flow Over a Rib

2014 ◽  
Author(s):  
Ebenezer E. Essel ◽  
Kathryn Atamanchuk ◽  
Samuel d’Auteuil ◽  
Mark F. Tachie
Keyword(s):  
Reynolds Number ◽  
Channel Flow ◽  
Open Channel ◽  
Low Reynolds Number ◽  
Open Channel Flow ◽  
Recirculation Region ◽  
Particle Image Velocimetry Technique ◽  
Mean Velocity ◽  
Freestream Velocity ◽  
Low Reynolds

An experimental study was conducted to investigate low Reynolds number effects on open channel flow over a transverse square rib. Particle image velocimetry technique was used to perform detailed velocity measurement in the upstream and recirculation region of a square rib of height, h = 12 mm. The Reynolds number based on the freestream velocity and rib height, Reh = 1510, 2650 and 3950 and the ratio of the boundary layer thickness to step height, δ/h = 2.5 ± 0.2. The results showed that the reattachment length of Reh = 2650 and 3950 increased by 5.7% compared with corresponding value of Reh = 1510. The mean velocities were independent of Reynolds number in the recirculation region but at the reattachment point, Reh = 3650 reduced the streamwise mean velocity and enhanced the wall-normal mean velocity in the region adjacent to the wall. The turbulent kinetic energy beyond the center of the recirculation region increased with increasing Reynolds number.

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