Long-time persistence of hydrodynamic memory boosts microparticle transport

TL;DR

This paper demonstrates that hydrodynamic memory effects in viscous fluids significantly influence microparticle transport, allowing particles to coast over potential barriers and reducing effective friction, with implications for nonequilibrium systems.

Contribution

It reveals that hydrodynamic memory effects persist indefinitely and substantially alter particle transport dynamics under general driving conditions.

Findings

Memory effects lower transport friction in non-smooth driving

Particles can coast over potential barriers due to memory effects

Hydrodynamic memory influences nonequilibrium microparticle transport

Abstract

In a viscous fluid, the past motion of an accelerating particle is retained as an imprint on the vorticity field, which decays slowly as $t^{-3/2}$. At low Reynolds number, the Basset-Boussinesq-Oseen (BBO) equation correctly describes nonuniform particle motion, capturing hydrodynamic memory effects associated with this slow algebraic decay. Using the BBO equation, we numerically simulate driven single-particle transport to show that memory effects persist indefinitely under rather general driving conditions. In particular, when driving forces do not vary smoothly, hydrodynamic memory substantially lowers the effective transport friction. Remarkably, this enables coasting over a spatially uneven potential that otherwise traps particles modeled with pure Stokes drag. Our results provide direct physical insight into role of particle-fluid coupling in nonequilibrium microparticle transport.