When an obstacle moves through a compressible medium, it creates a density perturbation. Theoretical arguments regarding the shape of this density wake in Brownian suspensions either suppose infinite dilution or describe only the far field. Here, we study via experiments and numerical simulations the closing of the density perturbation just behind a circular obstacle in dense 2D suspensions of particles that are thermal or self-propelled. In the thermal case, we show that the characteristic length of the wake is a non-monotonic function of density, decreasing then increasing. We rationalise the scalings of both regimes by analytical arguments that highlight the role of the compressibility factor of the suspension. Based on this new understanding of the passive case, we show that the influence of self-propulsion observed in experiments and simulations can be understood as if the obstacle is effectively larger in an active bath, with non-trivial and distinct roles of the self-propulsion velocity and of the persistence time.
Active Brownian particles confined to rigid substrates are known to accumulate near rigid boundaries and, under suitable conditions, undergo motility-induced phase separation (MIPS). A particularly intriguing manifestation of this behavior is the formation of self-sustained vortices around circular obstacles, which act...
Felipe P. S. Júnior, F. Potiguar, Jorge L. C. Domingos et al.· 0 citations
Abstract Content of image described in text. We explored the collective sedimentation of non-convex ring-shaped particles in viscous suspensions using direct numerical simulations based on the smoothed profile method. The toroidal particle geometry introduces an internal flow pathway that allows fluid penetration, fund...
Bilal Fareed, Muhammad Nadeem, Soohyeon Kang et al.· Journal of Fluid Mechanics· 0 citations
In this study, a two-dimensional lattice Boltzmann method is employed to numerically investigate the collective dynamics of squirmer–passive particle mixtures in a channel filled with power-law fluids. Particular attention is paid to the effects of the power-law index n, propulsion type β, and squirmer fraction c on th...
This paper presents a numerical study of the stability of a polymer solution flow between concentric cylinders with a rotating inner cylinder. The case of a small-radius inner cylinder is considered. The fluid motion is described using a specific case of the Kelvin-Voigt model, often referred to as the Oskolkov model....
Micron-sized particles moving through a fluid are subject to viscous resistance and thermal fluctuations. Beyond steady Stokes friction, colloids also exhibit hydrodynamic memory effects arising from conservation laws of the surrounding fluid. Although fluid-flow problems in complex geometries and confinements are ofte...
Benjamin Sorkin, Gunther Turk, Howard A. Stone· 2 citations
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