Sørensen Lasse, Bentzen Thomas Ruby
Department of Civil Engineering, Aablorg University, Aalborg Øst, Denmark E-mail:
Water Sci Technol. 2018 Dec;78(10):2077-2087. doi: 10.2166/wst.2018.478.
Fluid dynamics is used for fouling mitigation in membrane bioreactors (MBRs), whereby a proper understanding of the fluid dynamics is of great interest. The influence of fluid dynamics has led to the use of computational fluid dynamics for optimizing MBR systems. In this work, a model has been validated for flat sheet membranes, with use of the Eulerian multiphase method. The model is validated against a comparable setup where the liquid velocities are measured with a laser Doppler anemometer (LDA). Furthermore, the Eulerian multiphase approach is validated against the more numerical direct volume of fluid (VOF) approach with sludge properties for the liquid, resulting in an error between the models of less than 2% for the wall shear stresses. The VOF model further showed that the horizontal components contribute significantly to the total wall shear stresses. The model has been applied to a full-scale setup for studying the effect of deflecting membranes as deflections have been seen in production. Minimizing the deflection of the membrane sheets was crucial to achieve a good operating condition as a deflection of 2 mm in a setup with a gap of 7 mm decreased the wall shear stresses with as much as 40% on average on the specific membrane surface.
流体动力学被用于膜生物反应器（MBR）中的污垢减缓，因此，正确理解流体动力学具有重要意义。流体动力学的影响促使人们使用计算流体动力学来优化MBR系统。在这项工作中，使用欧拉多相方法对平板膜模型进行了验证。该模型是针对一个类似装置进行验证的，在该装置中使用激光多普勒测速仪（LDA）测量液体速度。此外，针对更具数值性的流体体积（VOF）方法对液体的污泥特性进行了验证，结果表明，两种模型之间的壁面剪应力误差小于2%。VOF模型进一步表明，水平分量对总壁面剪应力有显著贡献。该模型已应用于一个全尺寸装置，以研究膜片偏转的影响，因为在生产中已经观察到膜片的偏转。在间隙为7 mm的装置中，膜片偏转2 mm会使特定膜表面的壁面剪应力平均降低多达40%，因此将膜片的偏转最小化对于实现良好的运行条件至关重要。
