【作者】 李锟；

【导师】 黄卫东；

【作者基本信息】 中国科学技术大学 ， 环境工程， 2011， 硕士

【摘要】 .氧化沟的水力学特征对其设计和运行起着非常重要的作用,利用计算流体力学研究氧化沟,有利于了解氧化沟中的流动形态。本研究以倒伞型表面曝气机驱动的氧化沟为研究对象,对现有的动量源项模型进行改进,假设动量源项来自流体被叶轮作用增加的速度,考虑叶轮和流体之间的摩擦作用,修正了先前提出的动量源项模型,同时提出了一种预测功率方法及评价倒伞曝气机推流性能的方法。我们使用试验数据对模型进行了验证。首先,已有的动量源项模型(Model I)和经过改进的两种动量源项模型(Model II和Model III)分别被用来模拟涡轮搅拌槽流场,数值计算结果与大量报道的实验数据进行比较,并与多重参考系法和滑移网格法进行比较,结果表明改进后的模型Model III与实验值的吻合最好,是一种可靠的预测方法,提出的预测功率方法是可行的。而后,采用Model III来模拟倒伞驱动的试验氧化沟流场,比较不同的湍流模型和叶轮模型,并进行实验验证,进一步证明Model III能够用来模拟倒伞曝气机驱动的氧化沟流场,并且功率的预测方法是可行的。最后,利用动量源项Model III模拟不同倒伞的流场,比较它们的推流性能,并预测了一座全尺度卡鲁赛尔氧化沟在不同工况下的流速分布。更多还原

【Abstract】 The hydrodynamic characteristics play significant roles in design and operation of oxidation ditches. With the help of computational fluid dynamics (CFD), the hydrodynamic characteristics of oxidation ditches can be understood. In this study, based on numerical simulation of the inverse umbrella surface aerator in the oxidation ditch, the developed momentum source term model has been improved, then a method of predicting the power of the surface aerator and a way to value the propelling performance of the surface aerator have been proposed. First of all, the existing momentum source term model (Model I) and two improved momentum source term model (Model II and Model III) were used to investigate the flow characteristics in a Rushton turbine stirred vessel, then the calculated results were compared with the huge reported experimental data, as well as with the results simulated by multiple reference frame(MRF) and sliding mesh(SM), which showed the results of the improved momentum source term Model III were most agreed with the experimental data. It is suggested that Model III is a reliable approach and the proposed power predicting method is feasible. After that, Model III was used to simulate the flow field of the test oxidation ditch driven by an inverse umbrella surface aerator. The results from different turbulence models and impeller models were compared, as well as compared to the experimental data, which further proves that Model III can be applied to simulate the flow in oxidation ditch driving by the inverse umbrella surface aerator and the power of the aerator can be well predicted. In the end, on basis of the simulated flow field of the oxidation ditch driven by different inverse umbrella surface aerators, their propelling performances have been valued. Also, the flow distributions on several operating conditions of a full-scale carrousel oxidation ditch have been predicted with the Model III.更多还原