| Oxidation ditch is one of the most widely used water treatment technologyat present. The unique hydraulic characteristic of oxidation ditch directlyinfluences the terminal effect of sewage treatment. Due to the complex ofhydraulic conditions and high solid content in oxidation ditch, the phenomenonof sludge deposition often happens in regions lacking the driving force of flow,which affects the normal operation of oxidation ditch. The liquid-solidtow-phase flow simulation of oxidation ditch is a important method for thestudy of hydraulic characteristics and the prediction of position deposited sludgein oxidation ditch, which has important reference value for the optimization ofoxidation ditch.This paper established the mathematical relation between sludgeconcentration and sludge settling velocity that obeyed the Vesilind settlingmodel and the relation between sludge concentration and sludge viscosity thatobeyed the Hershel-Bulkley fluid model through experiments. The two-phaseturbulent model was coupled with sludge settling velocity model and sludgeviscosity model to achieve the settlement and viscosity changing of sludge.Taking Carrousel oxidation ditch as the research object, the distributions of flowfield and sludge concentration were simulated and analyzed based on thecomputational fluid dynamics software FLUENT. The reasonable measuringcross-sections were selected in oxidation ditch and the sludge concentration wasmeasured through the on-site test and compared with the simulation values ofsludge concentration on each measuring profile.The rotation speed of aerator directly determines the distributions of flowfield and sludge concentration in Carrousel oxidation ditch, which has a majoreffect on the normal operation of oxidation ditch and the effluent quality. On thecondition of different rotation speed of aerator, the mixing situation anddistribution of sludge concentration in oxidation ditch was simulated andanalyzed based on the above model. The simulation results can providereferences for the optimization of the rotation speed of aerator and the energy saving of oxidation ditch’s operation. |
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