Modelling the transport of momentum and oxygen in an aerial-disk driven bioreactor used for animal tissue or cell culture

Abstract

This study considers the momentum transport and oxygen transfer in a modified stirred tank bioreactor. The design is novel in the sense that the impeller is positioned above the culture medium (instead of being suspended inside it). This design has potential benefits of enhanced gas transfer, reduced possibility of contamination, and better access to the culture medium. Computational fluid dynamics modelling is used to simulate the gas and fluid flow in the bioreactor. A rotation rate of 60 to 240 rpm (corresponding to the laminar regime) was adopted. Results show that the flow in the medium is swirl-dominant with an induced secondary flow in the meridional plane consisting of a steady and robust recirculation bubble. As the Reynolds number is increased beyond ~427, we observe the formation of an additional smaller toroidal-bubble at the bottom wall. This bubble bears some resemblance to the vortex breakdown topology commonly found in confined swirling flows. In terms of the oxygen distribution, oxygen transfer from the gaseous phase into the culture medium is enhanced through forced diffusion taking place across the air-medium interface. For the Reynolds number range studied there is clear dominance of convection over diffusion in the transport of oxygen from the air-medium interface and throughout the culture medium.