An automated single-particle tracker: application to characterization of non-azimuthal motion in Couette flows at low Reynolds number |
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Authors: | O?Blaj P?Merzeau P?Snabre Email author" target="_blank">B?PoulignyEmail author |
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Institution: | (1) Centre de recherche Paul-Pascal, CNRS, University of Bordeaux, 33600 Pessac, France; |
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Abstract: | We describe an experiment that allows us to record 3-dimensional trajectories of single particles in Couette shear flows,
at low Reynolds number. The core of the apparatus is a Couette cell with transparent contra-rotating cylinders. Fluorescent
spherical particles are used as tracers. A single tracer is imaged onto a webcam, equipped with a home-made autofocus system.
For a given average shear rate, tracking of an individual tracer is performed automatically by driving the amount of contra-rotation
between both cylinders and the position of the webcam. The performance of the tracker is illustrated through examples of trajectories
of neutrally buoyant tracers in a Newtonian fluid. The setup is mostly aimed at characterizing complex flows in non-colloidal
concentrated suspensions and wet granular materials. We show examples of 3d trajectories in a dense suspension of 200 μm spherical
grains, revealing details of the short-scale diffusive-like particle motion, together with flow localization and large-scale
non-azimuthal flow patterns. |
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Keywords: | |
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