Numerical investigation of confined active collective motion in a viscoelastic fluid
Phys. Rev. E 114, 045101 – Published 7 October, 2026
DOI: https://doi.org/10.1103/msrn-mb3r
Abstract
Active fluids, which consist of self-propelling constituent units, often exhibit viscoelastic behavior. Building upon the mean-field kinetic theory, we incorporate the Oldroyd-B constitutive equation to investigate the collective motion of active particles in a viscoelastic fluid inside a circular chamber. Specifically, by introducing both a viscoelastic stress term and an active stress term into the Navier-Stokes equations, we study spontaneous flow states and their transitions. Our results show that the addition of elasticity destabilizes the active suspension and thus promotes phase transitions. The influence of viscoelasticity is most pronounced in regimes that are critical for transitions in the Newtonian case. We further analyze the accumulation of particles near the wall and find that the viscoelastic environment enhances both the wall-directed swimming speed and the steady-state wall accumulation, which increases monotonically with the Deborah number. Extending the computational framework of Theillard et al. [Soft Matter 13, 363 (2017)], this study elucidates how viscoelastic stresses modulate collective motion under confinement and offers new insights into the behavior of active collective systems.
