scholarly journals A Numerical Study on Influent Flow Rate Variations in a Secondary Settling Tank

Processes ◽  
2019 ◽  
Vol 7 (12) ◽  
pp. 884
Author(s):  
Junwei Su ◽  
Le Wang ◽  
Yumin Zhang ◽  
Zhaolin Gu
Keyword(s):  
Flow Rate ◽  
Numerical Study ◽  
Settling Tank ◽  
Two Phase ◽  
Sedimentation Tank ◽  
Secondary Settling ◽  
The Right ◽  
Solid Liquid ◽  
Changes Over Time ◽  
Influent Flow

The secondary settling tank is an essential unit for the biochemical treatment of domestic sewage, and its operational effect influences the quality of effluent. Under the influence of the confluence of rainwater and sewage, wastewater use habits, etc., the inflow of the secondary sedimentation tank changes over time. In this paper, OpenFOAM, an open-source computational fluid dynamics package, was used to study the dynamic behaviors of solid–liquid two-phase flow in the tank under influent flow rate variations. A coupled method including a mixture model, drift equation and a dynamic boundary method is proposed. Numerical investigations were carried out for a 2D axisymmetric sedimentation tank using 12 cases. With increasing influent flow rate, sludge accumulates continuously in the bottom left side of the tank, sludge hopper, and inlet; the sludge blanket thickness near the right end of the tank increases continuously; and the sludge concentration in the tank approximately linearly increases with time, with a low slope. The developed framework is generic and is, therefore, expected to be applicable for modelling sludge sedimentation processes.

scholarly journals Numerical Analysis of Single-Particle Motion Using CFD-DEM in Varying-Curvature Elbows

2022 ◽  
Vol 10 (1) ◽  
pp. 62
Author(s):  
Chao Ning ◽  
Yalin Li ◽  
Ping Huang ◽  
Hongbo Shi ◽  
Haichao Sun
Keyword(s):  
Single Particle ◽  
Particle Motion ◽  
Numerical Study ◽  
Area Ratio ◽  
Centrifugal Pumps ◽  
Distribution Law ◽  
Two Phase ◽  
Curvature Ratio ◽  
Critical Components ◽  
Solid Liquid

Centrifugal pumps are the critical components in deep-sea mining. In order to investigate the particle motion in the curved channel of the impeller, three different types of curvature conform to blade profile to simplify the impeller design of pumps. A numerical study is conducted to investigate the flow field in a varying-curvature channel for solid-liquid two-phase flow. The flow of particles within the varying curvature channel is studied by combining the discrete element method (DEM) with computational fluid dynamics (CFD) and a comparison with Particle Image Velocimetry (PIV) test results. The results show that a polyhedral mesh with a small mesh number yields very accurate results, which makes it very suitable for CFD-DEM. Based on this method, the movement of a single particle is compared and analyzed, and the particle-motion law is obtained. The effects of the curvature ratio Cr and area ratio Ar on the motion law for a single particle are studied, and the simulation results are analyzed statistically. The results show that the effect of Cr on both the particle slip velocity and the turbulent kinetic energy only changes its strength, while the distribution law does not change significantly. Compared with the curvature ratio Cr, the area ratio Ar has a greater impact on the particles, and its distribution law becomes clearly different. As the area ratio Ar increases, the arc radius and length of the corresponding particle trajectory decrease.

scholarly journals Numerical Study of Bubble Rising and Coalescence Characteristics under Flow Pulsation Based on Particle Method

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Ronghua Chen ◽  
Minghao Zhang ◽  
Kailun Guo ◽  
Dawei Zhao ◽  
Wenxi Tian ◽  
...  
Keyword(s):  
Flow Rate ◽  
Two Phase Flow ◽  
Flow Instability ◽  
Numerical Study ◽  
Phase Flow ◽  
Flow Pulsation ◽  
Two Phase ◽  
Inlet Flow ◽  
Inlet Flow Rate ◽  
Bubble Rising

Two-phase flow instability may occur in nuclear reactor systems, which is often accompanied by periodic fluctuation in fluid flow rate. In this study, bubble rising and coalescence characteristics under inlet flow pulsation condition are analyzed based on the MPS-MAFL method. To begin with, the single bubble rising behavior under flow pulsation condition was simulated. The simulation results show that the bubble shape and rising velocity fluctuate periodically as same as the inlet flow rate. Additionally, the bubble pairs’ coalescence behavior under flow pulsation condition was simulated and compared with static condition results. It is found that the coalescence time of bubble pairs slightly increased under the pulsation condition, and then the bubbles will continue to pulsate with almost the same period as the inlet flow rate after coalescence. In view of these facts, this study could offer theory support and method basis to a better understanding of the two-phase flow configuration under flow pulsation condition.

Numerical Study of Laminar Mixed Convection of a Nanofluid in a Horizontal Curved Tube with Constant Heat Flux and Mass Flow Rate

2011 ◽  
Vol 110-116 ◽  
pp. 3657-3662
Author(s):  
S. Alikhani ◽  
A. Behzadmehr ◽  
S. Mirmasoumi
Keyword(s):  
Heat Flux ◽  
Mixed Convection ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Volume Fraction ◽  
Numerical Study ◽  
Two Phase ◽  
Curved Tube ◽  
Laminar Mixed Convection

Fully developed laminar mixed convection of a nanofluid (water/Al2O3) in a horizontal curved tube is numerically investigated. Three-dimensional elliptic governing equations have been solved to show how nanoparticle concentration affects on thermal and hydrodynamic parameters while these parameters are impressed by centrifugal and buoyancy forces under constant mass flow rate and heat flux. Comparisons with previously published experimental works on horizontal curved tubes show good agreements between the results. Results which are obtained using the two – phase mixture model indicate that adding the nanoparticles causes changes in the properties of nanofluid and finally increases the temperature of the flow. Furthermore, increasing nanoparticles volume fraction at first augments the heat transfer coefficient of nanofluid and then, for higher concentration of particles, decreases this thermal parameter of nanofluid.

Measurement of flow rate in solid-liquid two-phase flow in pipes at low volume concentration with venturimeter

Measurement ◽  
2019 ◽  
Vol 138 ◽  
pp. 409-415
Author(s):  
Liyan Wang ◽  
Saiwei Li ◽  
Ye Yuan ◽  
Zhiqiang Sun ◽  
Tian Zhou
Keyword(s):  
Flow Rate ◽  
Volume Concentration ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Low Volume ◽  
Solid Liquid

The numerical study of transient flow in rotor and stator cascades of solid-liquid two-phase flow

2014 ◽  
Author(s):  
Wei Han ◽  
Rennian Li ◽  
Ting Yue ◽  
Vi Jin ◽  
Jiang Lei ◽  
...  
Keyword(s):  
Transient Flow ◽  
Two Phase Flow ◽  
Numerical Study ◽  
Phase Flow ◽  
Two Phase ◽  
Solid Liquid

Study on the Interference Ratio of Right-Turning Vehicles at Signalized Intersection under Mixed Traffic Environment

2011 ◽  
Vol 267 ◽  
pp. 555-560
Author(s):  
Shan Shan Lee ◽  
Da Lin Qian ◽  
Dong Mei Lin ◽  
Zhao Yong Peng
Keyword(s):  
Flow Rate ◽  
Wave Theory ◽  
Signalized Intersection ◽  
Motor Vehicles ◽  
Delay Model ◽  
Two Phase ◽  
Proposed Model ◽  
Traffic Wave ◽  
The Right ◽  
Bicycle Lane

The objective is to describe the interference degree between motor vehicles and bicycles at signalized intersection. The interference degree was expressed by conflict delay. Via analyzing the microscopic actions of the motor vehicles crossing through the bicycle flow at a typical two-phase signalized intersection, a conflict delay model of the right-turn vehicle was proposed applying the gap acceptance theory and traffic wave theory. The model was verified and compared with the existing conflict delay models. The result showed that the proposed model is stable and suitable for the condition of unsaturated to calculate the conflict delay of right-turn vehicle. Sensitivity of the conflict delay model with respect to the flow rate of the bicycle and the width of the bicycle lane was analyzed. It showed that the increase of the width of the bicycle lane within limits could reduce right-turning vehicle’s conflict delay effectively when the motor vehicle’s flow rate was higher and the bicycle flow rate was varying in a certain range.

A CFD Methodology for Solid and Liquid Flow Fields of Sedimentation Tanks

2012 ◽  
Vol 178-181 ◽  
pp. 371-375
Author(s):  
Y. L. Liu ◽  
Y. Zheng ◽  
P. Zhang ◽  
W.L. Wei
Keyword(s):  
Energy Dissipation ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Dissipation Rate ◽  
Concentration Distribution ◽  
Energy Dissipation Rate ◽  
Two Phase ◽  
Sedimentation Tank ◽  
Solid Distribution ◽  
Solid Liquid

In this paper, the CFD approach is used to study the solid–liquid two-phase turbulent flow and sludge concentration distribution in a secondary sedimentation tank. By the simulation, the velocity and the turbulent kinetic energy and turbulent kinetic energy dissipation rate and solid distribution in a secondary sedimentation tank are obtained, which shows the simulation model is an effective method to investigate the flow patterns and their influence on the process inside the sedimentation vessel.

Eulerian–Eulerian solid–liquid two-phase flow of sandstone wastewater in a hydropower station rectangular sedimentation tank

2013 ◽  
Vol 17 (8) ◽  
pp. 700-719 ◽  
Author(s):  
Xiaoling Wang ◽  
Ruirui Sun ◽  
Xuefei Ao ◽  
Zhengyin Zhou ◽  
Jian Lang
Keyword(s):  
Two Phase Flow ◽  
Hydropower Station ◽  
Phase Flow ◽  
Two Phase ◽  
Sedimentation Tank ◽  
Solid Liquid

scholarly journals Numerical Simulation Prediction of Erosion Characteristics in a Double-Suction Centrifugal Pump

Processes ◽  
2021 ◽  
Vol 9 (9) ◽  
pp. 1483
Author(s):  
Xijie Song ◽  
Dunzhe Qi ◽  
Lijuan Xu ◽  
Yubin Shen ◽  
Wei Wang ◽  
...  
Keyword(s):  
Flow Rate ◽  
Erosion Rate ◽  
Particle Concentration ◽  
Yellow River ◽  
Centrifugal Pumps ◽  
Two Phase ◽  
Pressure Surface ◽  
Motion Characteristics ◽  
Solid Liquid ◽  
The Impact

The double-suction centrifugal pumps installed along the Yellow River in China face serious sediment erosion due to the high sediment content which causes the poor operation efficiency of the pump units. The particle motion characteristics and erosion characteristics in a pump under different flow rates and different particle concentrations were numerically simulated based on the particle track model of solid-liquid two-phase flow. The results show that the flow rate has a significant effect on the particle tracks and the erosion caused by the particles in the impeller. The total erosion rate is positively correlated with the flow rate, and increases with the increase in flow rate. The vortex and secondary flow in the impeller have obvious influence on the particle trajectory, which increases the particle concentration at the trailing edge of the pressure surface and intensifies the impact erosion in this area. The particles carried by the vortex intensifies the local erosion. The particle concentration mainly affects the erosion rate, but has little effect on the erosion position. The influence of flow rate on pump erosion is greater than that of the particle properties. These results provide a reference for optimization of the design of anti-erosion blades of double-suction pumps and the regulation and operation of pumping stations.

The Lifting Efficiency of Coarse Particles in Vertical Pipes

2011 ◽  
Vol 66-68 ◽  
pp. 1219-1224
Author(s):  
Hua Chen Pan ◽  
Xiao Qing Tian ◽  
Lei Wu
Keyword(s):  
Average Velocity ◽  
Numerical Study ◽  
Solid Particles ◽  
Phase Flow ◽  
Coarse Particles ◽  
Two Phase ◽  
Average Speed ◽  
Solid Liquid ◽  
Moving Liquid ◽  
Pipe Vibration

A numerical method has been developed to analyze the solid-liquid two-phase flow with coarse particles in vertical pipes. Based on the numerical study, a concept of lifting efficiency has been suggested to describe the efficiency of lifting solid particles by the moving liquid. The lifting efficiency can be defined as, where vs is the average velocity of the solid particles and vl is the average speed of the liquid. It was found that when the liquid speed is lower than 3m/s, the lifting efficiency is increased when the liquid speed is increased. On the other hand if the liquid speed is more than 3m/s, the lifting efficiency will decrease if the liquid speed increases. It was also found that the speed of the particles will decrease if pipe vibration frequency is increased. However the lifting efficiency remains unchanged compared with the stationary pipes.

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