Is the zero Reynolds number approximation valid for ciliary flows?

Da Wei, Parviz Ghoddoosi Dehnavi, Marie Eve Aubin-Tam, Daniel Tam

Research output: Contribution to journalArticleScientificpeer-review

14 Citations (Scopus)
123 Downloads (Pure)


Stokes equations are commonly used to model the hydrodynamic flow around cilia on the micron scale. The validity of the zero Reynolds number approximation is investigated experimentally with a flow velocimetry approach based on optical tweezers, which allows the measurement of periodic flows with high spatial and temporal resolution. We find that beating cilia generate a flow, which fundamentally differs from the stokeslet field predicted by Stokes equations. In particular, the flow velocity spatially decays at a faster rate and is gradually phase delayed at increasing distances from the cilia. This indicates that the quasisteady approximation and use of Stokes equations for unsteady ciliary flow are not always justified and the finite timescale for vorticity diffusion cannot be neglected. Our results have significant implications in studies of synchronization and collective dynamics of microswimmers.

Original languageEnglish
Article number124502
Number of pages5
JournalPhysical Review Letters
Issue number12
Publication statusPublished - 2019


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