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The rich life of light rising spheres

Lieu, Alice and Auguste, Franck and Magnaudet, Jacques The rich life of light rising spheres. In: 66th APS DFD Annual Meeting, 24 November 2013 - 26 November 2013 (Pittsburgh, United States).

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Official URL: http://meetings.aps.org/Meeting/DFD13/Event/203471

Abstract

The straight path of spheres falling or rising in a weakly viscous fluid is known to become unstable beyond a critical value of the so-called Archimedes number Ar, a Reynolds number built on the gravitational velocity scale. Various styles of non-vertical paths have been reported so far: steady or oscillating oblique, planar zigzags, three-dimensional chaotic, etc. However despite careful computations and experiments, there is currently no consensus as regards the possible critical density ratio m* below which significant departures from straight (vertical or oblique) path are observed. To revisit this question, we carry out a detailed DNS study focused on rising spheres (m*\textless 1) in the range 150 ≤ Ar ≤ 350. Non-straight paths with significant horizontal excursions are observed throughout the whole range of m*. In addition to the various aforementioned types of paths we also identify other styles such as intermittent zigzagging/oblique paths and find that very light spheres describe highly nonlinear zigzags and have drag coefficients up to 15{\%} beyond standard values.

Item Type:Conference or Workshop Item (UNSPECIFIED)
Audience (conference):International conference without published proceedings
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - INPT (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UPS (FRANCE)
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Deposited By: Jacques MAGNAUDET
Deposited On:26 Nov 2013 15:22

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