| Oxidation ditch is oneof the most popular technologies in the field of wastewater treatment.The hydraulic regime of oxidation ditch is complex in the actual operation process,then it is easy to form the stagnant area and cause sludge deposition in the bending part and front and back straight section of the flow channel.The results will reduce the capacity utilization in the oxidation ditch and affect the quality of discharged water.In my paper,the three-dimensional numerical simulation of oxidation ditch flow field which was made by CFD software is used to research the flow characteristics of oxidation ditch.Based on the analysis of the three-dimensional flow characteristics of the oxidation ditch,this paper provides an effective reference for the design and operation of the oxidation ditch.In this paper,the RNG k-? turbulence model of oxidation ditch flow field with MRF model and SIMPLE algorithm was used to research the flow characteristics of oxidation ditch.First,this paper research the flow characteristics of oxidation ditch under two kinds of working condition which the aerator blade has been twisted for the angle of 30° provide The simulation results show that: when the aerator blade have been twisted for the angle of 30 ° of the water in the oxidation ditch are more fully;the area which the flow velocity is greater than 0.25 m/s is bigger and the sludge deposition area is smaller.In the second place,when the studysetsthe aerator blade has been twisted for the angle of 30° to simulate the flow pattern in oxidation ditch under the two kinds of conditions which the aerator is located in the middle of the oxidation ditch end and the downstream of the oxidation ditch end.The simulation results show that: when the surface aerator is located in the middle of the oxidation ditch end,the region when flow velocity over 0.25 m/s in the bottom of oxidation ditch is larger,and the sludge sedimentation occur rarely.The third place,the article fastened the aerator blade angle is 30 °.Under this condition,the effect on the flow regime of oxidation ditch was studied when the diversion wall have been set at the side of the aeration machine.The study found that,when setting the semicircular guide wall,the area behind the guide wall is easy to produce sludge accumulation,and the water flow rate is very low.So it is suggested that,the diversion wall is arranged in the middle of the flow passage or not to set.Finally,this paper set up the inside of the cross-sectional for the oxidation ditch was set for semicircle under r=1m,2m and 3m.The study found that the velocity in the oxidation ditch increases and the sludge is not easy to produce deposition.In this paper,the numerical simulation method is used to study the influence of various factors on the flow characteristics of oxidation ditch to avoid the bad conditions of the generation and save energy,which has an important predictive value for engineering practice. |
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