气泡浮力羽流动力特性三维数值模拟研究

Three-dimensional numerical simulation of dynamic characteristics of air bubble buoyancy plume

【目的】研究曝气池中气泡浮力羽流的动力特性,为提高深层曝气方式的污水处理效率提供依据。【方法】分别采用欧拉双流体模型和混合模型结合标准κ-ε紊流模型,对气泡浮力羽流进行数值模拟,讨论了这2种模型计算流场的精确性和边界条件的适应性,并使用压力隐式算子分裂PISO(Pressure-Implicit with splitting of operators)算法进行了速度与压力耦合求解。【结果】通过模拟得到了气泡羽流的瞬时性及其尾部的摆动规律等流动特性,模拟的速度矢量沿水深方向呈增加趋势,但表现并不稳定,在上部区域气泡羽流出现了摆动,而在下部区域气泡羽流的摆动不明显,但这一部分的速度相对较大。【结论】欧拉双流体模型结合标准κ-ε紊流模型模拟气泡浮力羽流动力特性优于混合模型。

[Objective] The dynamics of air bubble buoyancy plume in an aeration tank was studied to improve aeration wastewater treatment efficiency. [Method] In this paper, the dynamics of air bubble buoyancy plume was modeled using the Euler two-fluid model and the Mixture model with the standard κ-ε turbulent model, respectively. The accuracy of two multiphase flow models and the adaptability of boundary conditions were discussed. The Pressure-Implicit with splitting of operators （PISO） algorithm was used to solve velocity and pressure. [Result] Flow characteristics, including the instantaneous and the tailing swing of the air bubble plume were obtained. The increase of the computed velocity vector along the water-depth direction was unstable. Especially, in the upper region of the bubble plume appeared swing, while the oscillation of the bubble plume was not significant in the lower region with relatively larger velocity. [Conclusion] Euler two-fluid model with the standard turbulence model was better than the Mixture model when simulating the dynamic characteristics of bubble buoyancy plume.