scholarly journals Low relative-submergence effects in a rough-bed open-channel flow

2018 ◽  
Vol 57 (2) ◽  
pp. 139-166 ◽  
Author(s):  
Maxime Rouzes ◽  
Frédéric Yann Moulin ◽  
Emma Florens ◽  
Olivier Eiff
Keyword(s):  
Channel Flow ◽  
Open Channel ◽  
Open Channel Flow ◽  
Rough Bed

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.

Response of open-channel flow to a sudden change from smooth to rough bed

2022 ◽  
Author(s):  
Vijit Rathore ◽  
Nadia Penna ◽  
Subhasish Dey ◽  
Roberto Gaudio
Keyword(s):  
Channel Flow ◽  
Open Channel ◽  
Sudden Change ◽  
Open Channel Flow ◽  
Rough Bed

Spatially Averaged Open-Channel Flow over Rough Bed

2001 ◽  
Vol 127 (2) ◽  
pp. 123-133 ◽  
Author(s):  
Vladimir Nikora ◽  
Derek Goring ◽  
Ian McEwan ◽  
George Griffiths
Keyword(s):  
Channel Flow ◽  
Open Channel ◽  
Open Channel Flow ◽  
Rough Bed

scholarly journals A Meshless WCSPH Boundary Treatment for Open-Channel Flow over Small-Scale Rough Bed

2019 ◽  
Vol 2019 ◽  
pp. 1-17
Author(s):  
Yang Shi ◽  
Jiahua Wei ◽  
Shaowu Li ◽  
Peng Song ◽  
Bangwen Zhang
Keyword(s):  
Channel Flow ◽  
Open Channel ◽  
Polynomial Regression ◽  
Open Channel Flow ◽  
Turbulent Shear ◽  
Small Scale ◽  
Turbulent Shear Stress ◽  
Evolutionary Polynomial Regression ◽  
Boundary Treatment ◽  
Rough Bed

A weakly compressible smoothed particle hydrodynamics (WCSPH) method was developed to model open-channel flow over rough bed. An improved boundary treatment is proposed to quantitatively characterize bed roughness based on the ghost boundary particles (GBPs). In this model, the velocities of GBPs are explicitly calculated by using evolutionary polynomial regression with a multiobjective genetic algorithm. The simulation results show that the proposed boundary treatment can well reflect the influence of wall roughness on the vertical flow structure. A fully developed open channel is established, and its flume length, processing time, and turbulent model are discussed. The mixed-length-based subparticle scale (SPS) turbulence model is adopted to simulate uniform flow in open channel, and this model is compared with the Smagorinsky-based one. For the modified WCSPH model, the results show that the calculated vertical velocity and turbulent shear stress distribution are in good agreement with experimental data and fit better than the calculations obtained from the traditional Smagorinsky-based model.

Effect of aspect ratio on developing and developed narrow open channel flow with rough bed

2018 ◽  
Vol 45 (9) ◽  
pp. 780-794 ◽  
Author(s):  
Minakshee Mahananda ◽  
Prashanth Reddy Hanmaiahgari ◽  
Ram Balachandar
Keyword(s):  
Kinetic Energy ◽  
Aspect Ratio ◽  
Channel Flow ◽  
Open Channel ◽  
Reynolds Shear Stress ◽  
Open Channel Flow ◽  
Flow Region ◽  
Channel Flows ◽  
Open Channel Flows ◽  
Rough Bed

This study attempts to unravel the effect of aspect ratio on the turbulence characteristics in developing and fully developed narrow open channel flows. In this regard, experiments were conducted in a rough bed open channel flow. Instantaneous 3D velocities were acquired using an acoustic Doppler velocimeter at various locations along the centerline of the flume. The variables of interest include the mean components of the flow velocity, turbulence intensity, wall normal Reynolds shear stress, correlation coefficient, turbulence kinetic energy, and anisotropy. A new correlation between the equivalent roughness and velocity shift from the smooth wall logarithmic equation as a function of aspect ratio is proposed. Aspect ratio was found to influence the velocity characteristics throughout the depth in the developing flow region, while the effects are confined to the outer layer for fully developed flows. New equations to describe the variation of turbulence intensities and turbulent kinetic energy are proposed for narrow open channel flows. Reynolds stress anisotropy analysis reveals that level of anisotropy in narrow open channel flow is less than in wide open channel flows. Finally, a linear regression model is proposed to predict flow development length in narrow open channel flows with a rough bed.

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