
doi: 10.1017/jfm.2025.20
Cilia perform various functions, including sensing, locomotion, generation of fluid flows and mass transport, serving to underpin a vast range of biological and ecological processes. However, analysis of the mass transport typically fails to resolve the near-field dynamics around individual cilia, and therefore overlooks the intricate role of power/recovery strokes of ciliary motion. Selvan et al. (2023, Phys. Rev. Fluids8, 123103) observed that the flow field due to a point torque (i.e. a rotlet) accurately resolves both the near- and far-field characteristics of a single cilium’s flow in a semi-infinite domain. In this paper, we calculate the mass transport between a no-slip boundary and an adjacent fluid, as a model system for nutrient exchange with ciliated tissues. We develop a Langevin model in the presence of a point torque (i.e. a single cilium) to examine the nutrient flux from a localised surface source. This microscopic transport model is validated using a macroscopic continuum model, which directly solves the advection–diffusion equation. Our findings reveal that the flow induced by a point torque can enhance the particles’ transport, depending on their diffusivity and the magnitude of the point torque. Additionally, the average mass transport affected by a single cilium can be enhanced or diminished by the presence of an externally imposed linear shear flow, with a strong dependence on the alignment of the cilium. Taken together, this framework serves as a useful minimal model for examining the average nutrient exchange between ciliated tissues and fluid environments.
Biopropulsion in water and in air, advection-diffusion equation, cilia, mass transport, Stokes flow, average mass transport, localised surface source, locomotion, Langevin equation, Diffusion and convection, Langevin model, nutrient flux, Biomechanics, rotlet
Biopropulsion in water and in air, advection-diffusion equation, cilia, mass transport, Stokes flow, average mass transport, localised surface source, locomotion, Langevin equation, Diffusion and convection, Langevin model, nutrient flux, Biomechanics, rotlet
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