https://doi.org/10.1140/epjs/s11734-025-02057-1
Regular Article
Particle transport in oscillatory flows with streamwise nonuniformity: effects of particle inertia and thermal fluctuations
Department of Applied Mechanics and Biomedical Engineering, Indian Institute of Technology Madras, 600036, Chennai, India
a
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Received:
23
July
2025
Accepted:
31
October
2025
Published online:
10
November
2025
Abstract
We investigate the transport and dispersion of inertial particles in oscillatory flows with prominent streamwise flow variations—a hallmark of systems ranging from bifurcating lung airways to estuarine riverbeds. Using a one-dimensional dynamical framework, we systematically analyze the roles of particle inertia, flow nonuniformity, and thermal fluctuations, providing mechanistic understanding while avoiding the computational complexity of higher-dimensional models. A key novelty of our study is the finding that thermal fluctuations can suppress and reverse the direction of inertia-driven drift for small Stokes numbers under strong flow nonuniformity, particularly in deep breathing conditions, resulting in particle expulsion from the domain. Additionally, we identify a pronounced asymmetry in dispersion dependent on the breathing pattern: dispersion is suppressed during inhalation (when flow decelerates) and enhanced during exhalation (when flow accelerates), a phenomenon governed by the interplay of thermal noise and flow gradients. In the deterministic regime, we show that nonzero mean particle drift arises exclusively from the coupling of inertia and flow nonuniformity, with the drift magnitude decaying over successive cycles. Introducing thermal fluctuations disrupts this balance, leading to dispersion rates that depend critically on the direction and degree of flow variation. These findings resolve critical questions about oscillatory transport in systems with spatially varying flow and offer new quantitative insights into processes such as pathogen retention in lung airways and sediment dynamics in tidal flows. While the one-dimensional approach neglects transverse effects, its ability to isolate longitudinal mechanisms provides a foundational framework for understanding and optimizing transport in complex oscillatory environments.
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© The Author(s), under exclusive licence to EDP Sciences, Springer-Verlag GmbH Germany, part of Springer Nature 2025
Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
