Particle transport in flow through a ratchet-like channel
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We present a fluidic device that shows ratchet-like characteristics for particle transport at low Reynolds. The ratchet consists of a two-dimensional saw-tooth channel, within which a laminar flow is generated by imposing a longitudinal pressure gradient. Particle trajectories are calculated by solving the continuity and Navier–Stokes equations for the fluid flow and the equations for particle transport in both flow directions. The ratchet-like effect is connected with a large asymmetry in the mean transit time, with regard to flow direction, due to particle motion within zones of low flow velocity near the asymmetric wall profile. We show how to obtain ratchet of particles with select Stokes under given flow conditions by adjusting the geometry of the ratchet channel.
KeywordsParticles in fluids Particle transport Channel flow Ratchet effect
We acknowledge Antônio J. C. Sampaio for discussions and helpful comments. We also thank Josué Mendes Filho for stimulating remarks. This research was supported by CAPES, CNPq, FUNCAP and FINEP (Brazilian agencies), and CNPq/FUNCAP Pronex grant.
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