Tumbling of asymmetric microrods in a microchannel flow

Abstract

We describe results of measurements of the orientational motion of glass microrods in a microchannel flow, following the orientational motion of particles with different shapes. We determine how the orientational dynamics depends on the shape of the particle and on its initial orientation. We find that the dynamics depends so sensitively on the degree to which particle axisymmetry is broken that it is difficult to find particles that are sufficiently axisymmetric so that they exhibit periodic tumbling ("Jeffery orbits"). The results of our measurements confirm earlier theoretical analysis predicting sensitive dependence on particle shape and its initial orientation. Our results illustrate the different types of orientational dynamics for asymmetric particles predicted by theory.Comment: (a) These authors contributed equally to this work. 17 pages, 7 figures, 1 table, supplementary online materia

Effect of weak fluid inertia upon Jeffery orbits

“…C om parison w ith Eq. (7) shows that the contribution from convective fluid inertia is of the same order. For nearly spherical particles, by contrast, w e find that convective inertia dom inates (order e), w hile the contribution from unsteady fluid inertia is sm aller, o f order e2.…”

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Spinning and tumbling of micron-sized triangles in a micro-channel shear flow

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