Computational fluid dynamics simulations of Taylor bubbles in tubular membranes - Model validation and application to Laminar flow systems

The use of gas-liquid two-phase flow has been shown to significantly enhance the performance of some membrane processes by reducing concentration polarization and fouling. However, the understanding of the mechanisms behind gas-liquid two-phase flow enhancement of flux is still limited. This paper reports on the validation of computational fluid dynamics simulations of a Taylor bubble, using a variety of numerical approaches. Good agreement between the experimental and numerical data is shown for an Eulerian two-fluid model that uses a solution adaptive bubble size to avoid numerical mixing. This model is then used to study the effect of liquid extraction at the membrane wall on the wall shear stress, since it is the enhanced wall shear stress caused by the bubble passage that is important. This effect is shown to be negligible for typical operating conditions in membrane systems. Moreover, we show that the wall shear stress can be well represented by a 'top hat' profile for the system considered here.