横向流中曝气气泡生成动力学及模拟研究

采用水平集方法和变物性的单一流体运动方程,结合显式时间步进的ICE数值算法,三维模拟了推流式曝气池内气泡的生成过程.重点研究了横向水流对曝气气泡生成动力学的影响.模拟的气泡形状演变过程与国外学者的可视化实验符合较好.模拟结果显示,与在静止水流中气泡的生成相比,曝气池内水横向流动对气泡的生成过程有重要的影响.由于受到水流施加的横向曳力作用,气泡逐渐倾斜向下游生长;气泡生成的时间明显缩短;生成气泡的体积也显著地减小.

The dynamics of bubble formation through aeration with liquid cross-flow and its numerical simulation

A 3-dimensional numerical computation is carried out to simulate the process of bubble formation through aeration in a plug-flow aeration tank. The two-phase flow in aeration tank is treated as a single fluid with variable properties and the shape of bubble is traced by the level set method. An explicit time-marching ICE (Implicit Continuous-fluid Eulerian) algorithm is employed to solve the governing equations. The effects of the liquid cross-flow on dynamics of bubble formation in water are studied in detail. The simulation results on the bubble shape are qualitatively in good agreement with experimental observations in the literature. The results show that the liquid cross-flow has a strong impact on the bubble generation. When compared to bubble formation under quiescent liquid, the bubble grows downstream along the tilted axis, the bubble formation time tends to decrease noticeably, and the bubble formed has significantly smaller size due to the drag force acting on the forming bubble exerted by the liquid motion.