Active Darcy's Law

TL;DR

This paper introduces an active Darcy's law that models how active fluids, like bacterial swarms, flow through porous media, revealing an optimal activity level for maximum flow and explaining anomalous transport phenomena.

Contribution

It develops a new active Darcy's law incorporating activity effects, demonstrating flow enhancement and an optimal activity level in porous media.

Findings

Hybrid active/driven flows outperform pure-driven flows in drift.

Flow enhancement is non-monotonic with activity, showing an optimal point.

The model explains anomalous transport in swarming bacteria within porous environments.

Abstract

While bacterial swarms can exhibit active turbulence in vacant spaces, they naturally inhabit crowded environments. We numerically show that driving disorderly active fluids through porous media enhances Darcy's law. While purely active flows average to zero flux, hybrid active/driven flows display greater drift than pure-driven fluids. This enhancement is non-monotonic with activity, leading to an optimal activity to maximize flow rate. We incorporate the active contribution into an active Darcy's law, which may serve to help understand anomalous transport of swarming in porous media.