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Periodic and aperiodic tumbling of microrods advected in a microchannel flow

Journal article
Authors Jonas Einarsson
A. Johansson
S.K. Mahato
Yogeshwar Mishra
J. R. Angilella
Dag Hanstorp
Bernhard Mehlig
Published in Acta Mechanica
Volume 224
Issue 10
Pages 2281-2289
ISSN 0001-5970
Publication year 2013
Published at Department of Physics (GU)
Pages 2281-2289
Language en
Subject categories Physical Sciences


We report on an experimental investigation of the tumbling of microrods in the shear flow of a microchannel (dimensions: 40 mm x 2.5 mm x 0.4 mm. The rods are 20-30 mu m long and their diameters are of the order of 1 mu m. Images of the centre-of-mass motion and the orientational dynamics of the rods are recorded using a microscope equipped with a CCD camera. A motorised microscope stage is used to track individual rods as they move along the channel. Automated image analysis determines the position and orientation of a tracked rod in each video frame. We find different behaviours, depending on the particle shape, its initial position, and orientation. First, we observe periodic as well as aperiodic tumbling. Second, the data show that different tumbling trajectories exhibit different sensitivities to external perturbations. These observations can be explained by slight asymmetries of the rods. Third, we observe that after some time, initially periodic trajectories lose their phase. We attribute this to drift of the centre of mass of the rod from one to another streamline of the channel flow.

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