# Hydrodynamics of Confined Swimming: Persistence of Stokes Flow and Emergence of Boundary Layers

Bruno Ventéjou, Thibaut Métivet, Aurelie Dupont, Philippe Peyla

► To cite this version:

Bruno Ventéjou, Thibaut Métivet, Aurelie Dupont, Philippe Peyla. Hydrodynamics of Confined Swimming: Persistence of Stokes Flow and Emergence of Boundary Layers. DFD 2025 - 78th Annual Meeting of the APS Division of Fluid Dynamics, American Physical Society, Nov 2025, Houston (Texas), United States. pp.1-1. hal-05390358

HAL Id: hal-05390358

https://hal.science/hal-05390358v1

Submitted on 1 Dec 2025

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
# Hydrodynamics of Confined Swimming: Persistence of Stokes Flow and Emergence of Boundary Layers.

Bruno Ventéjou<fnref n="1" />, Thibaut Métivet<fnref n="2" />, Aurelie Dupont<fnref n="1" />, and
Philippe Peyla<fnref n="1" />

23/11/2025

Confinement significantly alters the hydrodynamics of swimming, yet its impact across different flow regimes remains incompletely understood. In this study, we explore how confinement influences swimming behavior, focusing primarily on the Stokes and laminar regimes. Using a minimal force model, we examine the local fluid velocity gradients to characterize the formation and thickness of the boundary layer ($\delta$) around the swimmer. Strikingly, we find that under strong confinement, the Stokes regime persists well beyond the classical Reynolds number threshold of unity, extending into higher-Re values without the emergence of inertial effects. In this regime, $\delta$ scales linearly with the fluid gap between the swimmer and the confining walls. However, beyond a critical confinement threshold, we observe the emergence of a confinement-independent boundary layer, signaling the onset of an inertial laminar regime. While fundamentally oriented, this work lays the foundation for understanding aquatic locomotion in restricted environments, with implications ranging from natural microhabitats to the design of micro-robots navigating the human body.

This project received financial support from the French National Research Agency (ANR-21-CE45-0005, FISHSIF project)

<footnote n="1">¹LIPhy, Université Grenoble-Alpes</footnote>

<footnote n="2">²ELAN, INRIA, Université Grenoble-Alpes</footnote>