| Oxidation ditch technology is widely used in urban sewage and industrial wastewater treatment for its simple and highly effective economic prominent advantages. Due to the big size, the flow field in the channel is very complicated and the flow velocity distribute uneven. Oxidation ditch in underpowered will cause local deposition of the sludge, and affect the normal operation of the oxidation ditch. The research for the fluid mechanics characteristics in oxidation ditch will provide solutions for the problems in oxidation ditch process, and has extremely significance for the design and operation.In this paper, using Pro/E and Fluent software, relying on a sewage plant of Wuhan DE oxidation ditch make the same size model with it. At the same time set up the 3D model of the oxidation ditch internal equipment through the Pro/E software, improved the previous numerical simulation that fan model was used to simulation the process of the underwater propeller. Make the simulation of DE oxidation ditch more consistent with the actual. The Sliding mesh technology,RNG k-? turbulence model and SIMPLEC pressure-velocity coupling were adopted in the Fluent simulation of the oxidation ditch flow flied. The result show that setting baffle can promote the vertical mixing of high flow and low water flow, the velocity distribution in oxidation ditch will be more uniform. And guide wall is set to avoid the flow near the corner wall appear stagnation and cyclotron, ensure the flow of water through the corner smoothly. The overall velocity distribution is relatively uniform, But a little low speed area exist in the oxidation ditch, low speed area mainly concentrated in the corner flow downstream of the guide wall on both ends. the flow velocity distribution of oxidation ditch under actual working condition is complex, different depth has the different velocity distribution. 2-D model has been unable to simulate the oxidation ditch accuratelyEstablished the mixing pool model with the underwater propeller, to simulate the flow flied of the large diameter underwater propeller at low speed and high speed small diameter diving blender under the swage-sediments two-phase flow, The two types of underwater propeller both can produce significant role in pushing flow, But the large diameter at low speed has the bigger stirring radius, the higher flow velocity of the overall pushing, the lower sedimentation rate of the sludge. Compared two kinds of propulsion equipment needed to power at the same time, in order to accept the same axial thrust condition, the result show that the large diameter of propeller need less power. The result show the large diameter mixer is more appropriate to push the sewage in the DE oxidation ditch.Numerical simulation results of the relevant model show that the guide wall eccentric setting is also necessity for DE oxidation ditch. The guide wall center should be set at the downstream. Its optimal eccentricity of guide wall is 0.5 m, the simulation results conform with the original design. In order to optimize the structure of the oxidation ditch, tried to extend the guide wall 3 m in the downstream direction, the result of simulation show this way did not improve the distribution of the flow fluid in the oxidation ditch. Set two guide wall in the oxidation ditch, the simulation results show that this way can reduce the low-speed zone in the oxidation ditch, offered a direction for the design of the oxidation ditch. |
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