Numerical Simulation of Free Surface and Flow Field Turbulence in a Circular Channel with the Side Weir in Subcritical Flow

2017 ◽  
Vol 18 (3-4) ◽  
pp. 255-267 ◽  
Author(s):  
Hamed Azimi ◽  
Saeid Shabanlou
Keyword(s):  
Numerical Simulation ◽  
Free Surface ◽  
Discharge Coefficient ◽  
Main Channel ◽  
Surface Discharge ◽  
Water Supply Systems ◽  
Circular Channel ◽  
Side Weir ◽  
Urban Sewage ◽  
Sharp Crest

AbstractWhen flow surface is higher than of a side weir crest, the overflow spilt over the crest and divert into a side channel. These structures are extensively used in urban sewage disposal networks, water supply systems, and drainage and flood diversion networks. This study simulates stream free surface, discharge over a sharp-crest side weir, and discharge coefficient of a side weir in a circular channel using FLOW-3D software. Numerical model results were compared with the experimental ones and the comparison proved an acceptable consistency between the numerical and experimental results. RNG k-ε turbulence model was used for simulating flow turbulence. The volume of fluid (VOF) method was used in this CFD analysis for predicting changes of flow free surface. Then, the numerical simulation results were examined for discharge coefficient of the side weir and flow free surface for different discharge passing through the main channel. The changes of dividing stream surface from main channel bed toward stream free surface were examined. The concluding section assessed the effect of shape of a circular channel on the pattern and intensity of a secondary flow in the main channel and the impacts of the discharge passing through the circular channel on height of stagnation point and shear stress pattern in the main channel bed.

Discharge and flow field of the circular channel along the side weir

2015 ◽  
Vol 42 (4) ◽  
pp. 273-280 ◽  
Author(s):  
Hamed Azimi ◽  
Hazhar Hadad ◽  
Zakarya Shokati ◽  
Mohammad Sajad Salimi
Keyword(s):  
Free Surface ◽  
Flow Field ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Circular Channel ◽  
Side Weir ◽  
Stream Surface ◽  
Discharge Coefficients ◽  
Drainage Networks ◽  
Surface Variation

The side weir is one of the most important hydraulic structures that is used by hydraulic engineers for adjusting and controlling flow in urban waste collection systems, irrigation and drainage networks. In this study, an equation is proposed for computing side weir discharge located on circular channels. The equation computes the side weir discharge with sufficient accuracy. Then, the RNG k–ε turbulence model is used for simulating the turbulence of the flow field and the free surface flow variations are modeled using volume of fluid scheme. Comparing experimental results with numerical simulations indicates acceptable accuracy of the numerical model. Also, the side weir discharge coefficients, flow free surface variation, behavior of dividing stream surface and variations of stagnation point height for different discharges within a circular channel along a side weir were examined.

Discharge Coefficient of Rectangular Side Weirs on Circular Channels

2016 ◽  
Vol 17 (7-8) ◽  
pp. 391-399 ◽  
Author(s):  
Hamed Azimi ◽  
Saeid Shabanlou ◽  
Isa Ebtehaj ◽  
Hossein Bonakdari
Keyword(s):  
Free Surface ◽  
Numerical Model ◽  
Flow Regime ◽  
Discharge Coefficient ◽  
Three Dimensional ◽  
Free Surface Flow ◽  
Energy Difference ◽  
Surface Flow ◽  
Side Weir ◽  
Supercritical Flow

AbstractIn this study, the flow turbulence and variations of the supercritical free surface flow in a circular channel along a side weir are simulated as three dimensional using the RNG k-ε turbulence model and volume of fluid (VOF) scheme. Comparison between the numerical model and experimental measurements shows that the numerical model simulates the free surface flow with good accuracy. According to the numerical model results, the specific energy variations along the side weir for the supercritical flow regime are almost constant and the energy drop is not significant but by increasing the side weir length the energy difference between the side weir upstream and downstream increases. Next, using the nonlinear regression (NLR) and analysis of the simulation results, some relationships for calculating the discharge coefficient of side weir on circular channels in supercritical flow regime are provided.

scholarly journals Equivalent Discharge Coefficient of Side Weirs in Circular Channel—A Lazy Machine Learning Approach

Water ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 2406 ◽  
Author(s):  
Granata ◽  
Nunno ◽  
Gargano ◽  
Marinis
Keyword(s):  
Machine Learning ◽  
Discharge Coefficient ◽  
Nearest Neighbor ◽  
Learning Algorithms ◽  
Machine Learning Algorithms ◽  
Circular Channel ◽  
K Nearest Neighbor ◽  
Side Weir ◽  
Input Variables ◽  
Side Weirs

Side weirs have been widely used since ancient times in many hydraulic works. Their operation can be analyzed following different approaches. However, almost all possible analysis approaches require knowledge of the discharge coefficient, which depends on several geometric and hydraulic parameters. An effective methodology for predicting discharge coefficient can be based on machine learning algorithms. In this research, experimental data obtained from tests carried out on a side weir in a circular channel and supercritical flow have been used to build predictive models of the equivalent discharge coefficient, by which the lateral outflow can be estimated by referring only to the flow depth upstream of the side weir. Four models, different in the input variables, have been developed. Each model has been proposed in 5 variants, depending on the applied algorithm. The focus is mainly on two lazy machine learning algorithms: k Nearest Neighbor and K-Star. The 5-input variables Model 1 and the 4-input variables Model 2 noticeably outperform the 3-input variables Model 3 and Model 4, showing that a suitable characterization of the side weir geometry is essential for a good accuracy of the prediction model. In addition, under models 1 and 2, k Nearest Neighbor and K-Star, despite the simpler structure, provide comparable or better performance than more complex algorithms such as Random Forest and Support Vector Regression.

Discharge coefficient of a broad crested side weir in an earthen channel

2013 ◽  
Vol 13 (1) ◽  
pp. 166-177 ◽  
Author(s):  
Mohammad Reza Namaee ◽  
Mohammad Sadegh Jalaledini ◽  
Mahdi Habibi ◽  
Saeed Reza Sabbagh Yazdi ◽  
Mona Ghafouri Azar
Keyword(s):  
Discharge Coefficient ◽  
Experimental Tests ◽  
Main Channel ◽  
Channel Width ◽  
Flow Depth ◽  
Irrigation Systems ◽  
Side Weir ◽  
Hydraulic Behavior ◽  
Side Weirs ◽  
Upstream Flow

Side weirs are widely used to divert flows from rivers and channels. However, the hydraulic behavior of this type of weir is complex and difficult to predict accurately. Previous studies on side weirs have generally focused on side weirs in rectangular channels with a smooth bed. However, one of the applications of side weirs is in irrigation systems which have trapezoidal cross sections and significant bed roughness. The present study investigates the hydraulic behavior of a broad crested side weir in an earthen channel with a rough bed under subcritical flow. These investigations showed that the side weir discharge coefficient is influenced by four main parameters which are upstream Froude number, ratio of the main channel width to the upstream flow depth, ratio of the length of the side weir to the main channel width and ratio of side weir height to the upstream flow depth. The results showed that the discharge coefficient of the side weir gives a lower coefficient value compared to other researchers’ equations. Nearly 90 experimental tests were carried out and finally new equations are proposed for prediction of discharge coefficient of a broad crested side weir in an earthen channel under subcritical conditions which can be mainly used in common irrigation systems.

Supercritical flow over a rectangular side weir

2003 ◽  
Vol 30 (3) ◽  
pp. 596-600 ◽  
Author(s):  
Masoud Ghodsian
Keyword(s):  
Discharge Coefficient ◽  
Hydraulic Characteristics ◽  
Height Ratio ◽  
Side Weir ◽  
Supercritical Flow ◽  
Urban Sewage ◽  
Land Drainage ◽  
Weir Height ◽  
Side Weirs ◽  
Sewage Systems

Side weirs are flow-diversion devices widely used in irrigation, land drainage, and urban sewage systems. Hydraulic characteristics of a sharp-crested rectangular side weir under supercritical flow have been studied in this paper. The concept of elementary discharge coefficient for supercritical flow is introduced. The elementary discharge coefficient has been related to head weir height ratio and local Froude number. Suitable equations for the elementary discharge coefficient are introduced.Key words: supercritical flow, sharp crested, rectangular side weir, elementary discharge coefficient.

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