Investigating Bacterial Motion Near Walls in Low Reynolds Number Non-Newtonian Fluids

Abstract

Bacterial motion in non-Newtonian fluids is influenced by ciliary propulsion modes (push/pull), fluid rheological properties, and wall effects, with the interaction of these factors resulting in diverse movement behaviors. However, the quantitative mechanisms by which these factors affect the average velocity of bacteria remain unclear. This study utilizes the COMSOL Multiphysics simulation platform to develop a rigid two-dimensional ellipsoidal bacterial model and conducts numerical simulations within a square micro-scale Carreau fluid domain. By introducing magnetic force constraints to inhibit near-wall adhesion, the study systematically explores the coupling effects of these factors. The results indicate that: (1) the ciliary propulsion mode primarily determines the average velocity, and fluid properties (relaxation time , power index ) significantly influence this velocity response; (2) wall constraint effects are pronounced, with the average velocity of bacteria in the -direction reduced by approximately 86% at a distance of 50 μm from the wall compared to the far-field value. This research provides a theoretical foundation for the active regulation of microbial motion in complex fluid environments.