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arXiv · 2509.16430

Transport barriers for microswimmers in unsteady flow

L. Storm·J. Qiu·K. Gustavsson·B. Mehlig
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Abstract

Certain flow structures trap active microorganisms over extended periods, impacting mortality and growth by inhibiting foraging, exploration, and predator evasion. We show that transport barriers and trapping of a microswimmer in unsteady vortex flow can be understood in terms of Lagrangian coherent structures (LCS) in phase space, taking into account both flow and swimming dynamics. These phase-space LCS constrain when and how artificial microswimmers can be trained by reinforcement learning to escape traps. Our results suggest that phase-space LCS can explain training failure and success in a broad class of navigation problems.

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L. Storm, J. Qiu, K. Gustavsson, B. Mehlig. 2025-09-19. Transport barriers for microswimmers in unsteady flow. https://arxiv.org/abs/2509.16430

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