Collective Behavior of Swimming Microorganisms in Viscoelastic Media

Suspensions of motile microorganisms, such as bacteria, are often associated with the viscoelastic behavior due to secretion of the extracellular polymeric substances. This phenomenon has a profound impact on the hydrodynamic interactions of swimming microorganisms and the resulting complex dynamics. To elucidate this process, we used a kinetic model developed to study the behavior of self-propelled particles in conjunction with Oldroyd-B constitutive equation and the Stokes equations. Numerical simulations of the system have been conducted to scrutinize the effect of the viscoelasticity on the large-scale coordinated behavior of the microorganisms. In addition, different regimes of the flow have been explored by varying the corresponding parameters of the problem, such as Weissenberg number and viscosity ratio, in order to shed light on the characteristics of the flow patterns induced by the collective motion of microscopic swimmers.