CFD for the influence of submergence depth of impellers on the flow field and sludge concentration distributions in an oxidation ditch

2020 ◽  
Vol 201 ◽  
pp. 86-94
Author(s):  
Wenli Wei ◽  
Ch. Wang ◽  
J. Wei ◽  
Y. Cai ◽  
Y. Chang ◽  
...  
Keyword(s):  
Flow Field ◽  
Oxidation Ditch ◽  
Submergence Depth ◽  
Sludge Concentration

scholarly journals Study on Propellers Distribution and Flow Field in the Oxidation Ditch Based on Two-Phase CFD Model

Water ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2506 ◽  
Author(s):  
Yuquan Zhang ◽  
Chengyi Li ◽  
Yanhe Xu ◽  
Qinghong Tang ◽  
Yuan Zheng ◽  
...  
Keyword(s):  
Flow Field ◽  
Activated Sludge ◽  
Wastewater Treatment Plants ◽  
Dead Zone ◽  
Production Costs ◽  
Oxidation Ditch ◽  
Cfd Model ◽  
Two Phase ◽  
Flow Field Characteristics ◽  
Increasing Demand

The oxidation ditch (OD) plays an important role in wastewater treatment plants. With increasing demand and production costs, the energy consumption and sludge deposition occurring in the OD must be diminished to enhance its development. In this paper, a two-phase computational fluid dynamics (CFD) model of water and activated sludge examined the flow field characteristics of an OD, consisting of two side-by-side propellers. The system was studied under five configurations, where the spacing between the propellers was set equal to −0.2, −0.1, 0, 0.1, 0.2 times the length of the OD. The viscosity and settling rate of activated sludge was imported in the numerical simulation through a user defined function (UDF). The optimal scheme of the propeller’s power consumption, velocity distribution, and sludge concentration distribution was obtained. The result shows that sludge concentrations are linked with dead zone velocity but not necessarily with low velocities. Experiments confirmed the validity of the velocity flow field simulated by the two-phase CFD model. Overall, these findings form the basis for the propellers distribution optimization and allow a deeper insight into the flow field of OD systems.

Optimization design of submerged propeller in oxidation ditch by computational fluid dynamics and comparison with experiments

2016 ◽  
Vol 74 (3) ◽  
pp. 681-690 ◽  
Author(s):  
Yuquan Zhang ◽  
Yuan Zheng ◽  
E. Fernandez-Rodriguez ◽  
Chunxia Yang ◽  
Yantao Zhu ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Energy Consumption ◽  
Flow Field ◽  
Flow Pattern ◽  
Operating Conditions ◽  
Oxidation Ditch ◽  
Actual Measurement ◽  
Operating Condition ◽  
Rotating Speed

The operating condition of a submerged propeller has a significant impact on flow field and energy consumption of the oxidation ditch. An experimentally validated numerical model, based on the computational fluid dynamics (CFD) tool, is presented to optimize the operating condition by considering two important factors: flow field and energy consumption. Performance demonstration and comparison of different operating conditions were carried out in a Carrousel oxidation ditch at the Yingtang wastewater treatment plants in Anhui Province, China. By adjusting the position and rotating speed together with the number of submerged propellers, problems of sludge deposit and the low velocity in the bend could be solved in a most cost-effective way. The simulated results were acceptable compared with the experimental data and the following results were obtained. The CFD model characterized flow pattern and energy consumption in the full-scale oxidation ditch. The predicted flow field values were within −1.28 ± 7.14% difference from the measured values. By determining three sets of propellers under the rotating speed of 6.50 rad/s with one located 5 m from the first curved wall, after numerical simulation and actual measurement, not only the least power density but also the requirement of the flow pattern could be realized.

Simulation on Three-Dimensional Flow Field of Oxidation Ditch

2012 ◽  
Vol 516-517 ◽  
pp. 1001-1005
Author(s):  
Wei Wei ◽  
Dun Qiu Wang ◽  
Jian Wen Wei ◽  
Hong Tao Zhou
Keyword(s):  
Mathematical Model ◽  
Flow Field ◽  
Three Dimensional ◽  
Oxidation Ditch ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Fluent Software ◽  
Simulation Results

Using the Fluent software, the flow field of oxidation ditch was simulated by the three dimensional turbulence mathematical model. The velocities were analyzed and measured, and the simulation results showed acceptable prediction of the velocities in the oxidation ditch. The results also showed that velocity could reach more than 0.3m/s when 8 impellers worked, and MLSS in the whole ditch were almost uniform, therefore, the oxidation ditch runs well.

Flow field prediction in full-scale Carrousel oxidation ditch by using computational fluid dynamics

2010 ◽  
Vol 62 (2) ◽  
pp. 256-265 ◽  
Author(s):  
Yin Yang ◽  
Yingying Wu ◽  
Xiao Yang ◽  
Kai Zhang ◽  
Jiakuan Yang
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Field ◽  
Full Scale ◽  
Hydrodynamic Performance ◽  
Cfd Modeling ◽  
Oxidation Ditch ◽  
Wall Model ◽  
Moving Wall ◽  
Carrousel Oxidation Ditch

In order to optimize the flow field in a full-scale Carrousel oxidation ditch with many sets of disc aerators operating simultaneously, an experimentally validated numerical tool, based on computational fluid dynamics (CFD), was proposed. A full-scale, closed-loop bioreactor (Carrousel oxidation ditch) in Ping Dingshan Sewage Treatment Plant in Ping Dingshan City, a medium-sized city in Henan Province of China, was evaluated using CFD. Moving wall model was created to simulate many sets of disc aerators which created fluid motion in the ditch. The simulated results were acceptable compared with the experimental data and the following results were obtained: (1) a new method called moving wall model could simulate the flow field in Carrousel oxidation ditch with many sets of disc aerators operating simultaneously. The whole number of cells of grids decreased significantly, thus the calculation amount decreased, and (2) CFD modeling generally characterized the flow pattern in the full-scale tank. 3D simulation could be a good supplement for improving the hydrodynamic performance in oxidation ditch designs.

Simulation of flow field and sludge settling in a full-scale oxidation ditch by using a two-phase flow CFD model

2014 ◽  
Vol 109 ◽  
pp. 296-305 ◽  
Author(s):  
Hao Xie ◽  
Jiakuan Yang ◽  
Yuchen Hu ◽  
Hao Zhang ◽  
Yin Yang ◽  
...  
Keyword(s):  
Flow Field ◽  
Two Phase Flow ◽  
Full Scale ◽  
Phase Flow ◽  
Oxidation Ditch ◽  
Cfd Model ◽  
Two Phase ◽  
Sludge Settling

scholarly journals Simulation on flow field and gas hold-up of a pilot-scale oxidation ditch by using liquid-gas CFD model

2018 ◽  
Vol 78 (9) ◽  
pp. 1956-1965 ◽  
Author(s):  
Qi Xu ◽  
Jiakuan Yang ◽  
Huijie Hou ◽  
Yuchen Hu ◽  
Sha Liang ◽  
...  
Keyword(s):  
Flow Field ◽  
Flow Velocity ◽  
Test Site ◽  
Pilot Scale ◽  
Operating Conditions ◽  
Oxidation Ditch ◽  
Cfd Model ◽  
Two Phase ◽  
Vof Model ◽  
Optimal Setting

Abstract A liquid–gas two-phase computational fluid dynamics (CFD) model was developed to simulate flow field and gas hold-up in a pilot-scale oxidation ditch (OD). The volume of fluid (VOF) model and the mass flow inlet boundary condition for gas injection were introduced in this model. The simulated values of the flow velocities and the gas hold-up were verified by experimental measurements in the pilot-scale OD. The results showed that the gas hold-up at test-site 3, immediately downstream of the surface aerator, was the highest among all three test-sites. Most of the gas existed in the upper portion of the ditch and was close to the inner side of the channel. Based on the liquid–gas two-phase CFD model, three operating conditions with different setting height ratios of the submerged impellers were simulated. The simulated results suggested that the setting heights of the submerged impellers have significant impacts on the flow velocity distribution. Lowering the setting height could increase the flow velocity in the pilot-scale OD. An optimal setting height ratio of 0.273 was proposed, which would be beneficial for minimizing sludge sedimentation, especially near the inner side of the curve bend.

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