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arXiv · 1902.05304

Enhanced velocity fluctuations in interacting swimmer suspensions

Sankalp Nambiar·Piyush Garg·Ganesh Subramanian
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Abstract

A dilute non-interacting suspension of micro-swimmers exhibits a finite velocity variance and short-ranged correlations that decay over a swimmer length. For a suspension of interacting straight swimmers, however, pair-interactions leads to a non-decaying velocity covariance, and a variance that diverges logarithmically with system size. The divergence is arrested on inclusion of orientation decorrelation mechanisms. Results for suspensions of run-and-tumble particles (RTPs) are presented, where the underlying straight-swimmer divergence leads to a broad cross-over between the ballistic and diffusive regimes, of immersed passive tracers, in the limit of long run lengths. Our analysis explains long-standing experimental observations of a volume-fraction dependent crossover time for passive tracer dynamics.

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Sankalp Nambiar, Piyush Garg, Ganesh Subramanian. 2019-12-24. Enhanced velocity fluctuations in interacting swimmer suspensions. https://doi.org/10.1017/jfm.2020.827

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