序批式反应器内多尺度三相流动的数值模拟

提出1个混合模型来数值模拟序批式反应器内气-液-固三相的多尺度流动.该混合模型采用Level Set方法模拟曝气气泡的运动,应用离散颗粒方法处理活性污泥固体的运动,运用体积平均的Navier-Stokes方程描述液相的流动.模型考虑了颗粒-气泡、颗粒-流体以及气泡-流体之间的相互作用.通过模拟反应器内曝气气泡生成、上升以及污泥沉淀的动态过程,检验了模型的可行性.流动结构的模拟结果显示,在反应器中污泥与污水均有明显的环流特征.气泡与颗粒相互作用引起的气泡破碎行为会导致反应器内大量小气泡的生成以及污泥颗粒的弥散.反应器内这些流体动力学特征使得污泥与污水达到充分混合,有利于生物降解处理.

Numerical simulation of multi-scale three-phase flows in a Sequencing Batch Reactor

A hybrid model is presented for three-dimensional simulation of multi-scale gas-liquid-solid flows in a sequencing batch reactor (SBR).This model describes the motion of the aeration bubble,continuous liquid phase and activated sludge solid phase,based on the level-set method,the volume-averaged Navier-Stokes equations,and the discrete particle approach.Various interactions of particle-bubble,gas-liquid,and particle-liquid are taken into account in the model.The validity of the simulation based on this model is examined through several typical dynamic processes including aeration bubble formation and rising,and sludge sedimentation in the SBR.The simulation results of flow structure reveal the internal circulation of the sewage and sludge with upward flow in the center region and downward flow near the wall in the SBR.Bubble breakage due to bubble-particle interaction results in the appearance of a number of small size bubbles and good dispersion of particles.These hydrodynamic characteristics make the sewage and activated sludge mix fully,which is favorable to the biodegradation process.