L. Böhm

The importance of fluid dynamics for MBR fouling mitigation

The importance of the multiphase fluid dynamics for fouling mitigation in MBR systems has been widely acknowledged with air sparging having been applied commercially for about 20 years. However, the effects of air scouring are still not fully understood since the transient orthogonal and parallel flows as well as turbulent eddies created by bubbling generate complex hydrodynamic flow fields in the vicinity of a membrane. There is no generally valid model that describes the relationship between fouling rate and fluid dynamics. So, a reliable and universally applicable model to optimize membrane module and tank geometries, air scouring and filtration cycles is still pending. In addition to providing a discussion on the importance of multiphase fluid dynamics for fouling control, this review aims at developing guidelines to choose appropriate experimental and numerical methods for fluid dynamics investigations in MBR systems.

Simulation of the Single Bubble Ascent with OpenFOAM

This project is motivated by the challenge of cleaning flat sheet membrane surfaces with the help of aeration. On the basis of earlier experiments and CFD simulations, a decision was made to use the CFD-tool OpenFOAM in contrast to earlier simulations which were performed with Ansys Fluent. In the new simulations, the advancing computing power allowed the simulation of a bubble ascent in the full channel which is of special interest in cases where the bubble size is smaller than the channel depths. Besides saving the licensing cost, OpenFOAM allows access to the source code and, therefore, easier implementation of sub-models if necessary.