Activity-induced clustering in model dumbbell swimmers: The role of hydrodynamic interactions

Abstract

Using a fluid-particle dynamics approach, we numerically study the effects of hydrodynamic interactions on the collective dynamics of active suspensions within a simple model for bacterial motility: each microorganism is modeled as a stroke-averaged dumbbell swimmer with prescribed dipolar force pairs. Using both simulations and qualitative arguments, we show that, when the separation between swimmers is comparable to their size, the swimmers' motions are strongly affected by activity-induced hydrodynamic forces. To further understand these effects, we investigate semidilute suspensions of swimmers in the presence of thermal fluctuations. A direct comparison between simulations with and without hydrodynamic interactions shows these to enhance the dynamic clustering at a relatively small volume fraction; with our chosen model the key ingredient for this clustering behavior is hydrodynamic trapping of one swimmer by another, induced by the active forces. Furthermore, the density dependence of the motility (of both the translational and rotational motions) exhibits distinctly different behaviors with and without hydrodynamic interactions; we argue that this is linked to the clustering tendency. Our study illustrates the fact that hydrodynamic interactions not only affect kinetic pathways in active suspensions, but also cause major changes in their steady state properties.

arXiv comment18 pages, 14 figures

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Cited by in corpus (13)

• Emergent behavior in active colloids
• Clustering of microswimmers: Interplay of shape and hydrodynamics
• Motility-induced phase separation and coarsening in active matter
• Fission and fusion scenarios for magnetic microswimmer clusters
• Phase behavior of active Brownian disks, spheres, and dumbbells
• Pressure of a gas of underdamped active dumbbells
• Dynamic Clustering in Suspension of Motile Bacteria
• Response of active Brownian particles to shear flow
• Hydrodynamics of polymers in an active bath
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• Phase Ordering in Binary Mixtures of Active Nematic Fluids
• Hydrodynamic interactions in anomalous rheology of active suspensions
• Recovery of mechanical pressure in a gas of underdamped active dumbbells with Brownian noise