A numerical analysis of effects of vortex breakdown on oxygen transport in a micro-bioreactor

Vortex breakdown effects on oxygen concentration distributions in a micro-bioreactor were investigated by a finite volume model. The bioreactor consists of a cylindrical chamber with a rotating bottom wall. The minimum oxygen concentration and volumetric oxygen transfer coefficient were summarized at different Reynolds numbers, Damkohler numbers as well as bioreactor aspect ratios. It was found that vortex breakdown extends the axis region where oxygen concentration is higher. Also vortex breakdown tends to induce a uniform oxygen concentration distribution in the bioreactor. Thus, the occurrence of vortex breakdown is of benefit to animal cell culture. Compared with that in the bioreactor with a rigid lid, vortex breakdown in the bioreactor with free surface may be better for animal cell culture as the bubble has larger size and may occur apart from the axis.