Simulations of Brownian tracer transport in squirmer suspensions

Blaise Delmotte (1) , Eric E Keaveny (2) , Éric Climent (3) , Franck Plouraboué (3)

1 Courant Institute of Mathematical Sciences, New York University, New York, NY, United States
2 Department of Mathematics [Imperial College London]
3 IMFT - Institut de mécanique des fluides de Toulouse

In addition to enabling movement towards environments with favourable living conditions, swimming by microorganisms has also been linked to enhanced mixing and improved nutrient uptake by their populations. Experimental studies have shown that Brownian tracer particles exhibit enhanced diffusion due to the swimmers, while theoretical models have linked this increase in diffusion to the flows generated by the swimming microorganisms, as well as collisions with the swimmers. In this study, we perform detailed simulations based on the force-coupling method and its recent extensions to the swimming and Brownian particles to examine tracer displacements and effective tracer diffusivity in squirmer suspensions. By isolating effects such as hydrodynamic or steric interactions, we provide physical insight into experimental measurements of the tracer displacement distribution. In addition, we extend results to the semi-dilute regime where the swimmer–swimmer interactions affect tracer transport and the effective tracer diffusivity no longer scales linearly with the swimmer volume fraction.

Mots clés: Tracer dispersion; Squirmers; Active suspensions; Simulations

Domaines: Milieux fluides et réactifs; Mécanique [physics.med-ph]; Mécanique des fluides [physics.class-ph]

Blaise Delmotte, Eric E Keaveny, Éric Climent, Franck Plouraboué. Simulations of Brownian tracer transport in squirmer suspensions. IMA Journal of Applied Mathematics, 2018, 83 (4), pp.680-699. ⟨10.1093/imamat/hxy012⟩. ⟨hal-02134650⟩