Numerical Simulation of Fluid Flow and Oxygen Transport in the Tube Flow Cells Containing Biofilms

The hydrodynamics in flow systems is known to induce phenotypic changes associated with bacterial biofilms, including increased tolerance to antimicrobial agents and biocides. Results obtained in flow cells commonly used in biological and medical studies on the influence of flow on biofilm behavior and antimicrobial susceptibility are sometimes contradictory. It is thus hypothesized that discrepancies in the results may be related to the flow cell geometry. In this study, the shear stress distribution and substrate concentration were numerically simulated inside long rectangular and square tubes. The fluid was Newtonian and a uniform distribution of biofilms, which consume the substrate from the medium, was assumed on the walls. The consumption of oxygen by biofilms was assumed to follow the Monod kinetics. The effects of flow velocity, flow cell geometry, and substrate diffusivity on wall shear stress and substrate concentration distributions were investigated. Based on simulation results, differences observed in the morphology and response of biofilms can be directly related to hydrodynamic changes caused by the flow cell configuration.