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The calculation of flow fields by panel methods: a report on Euromech 75

Published online by Cambridge University Press:  11 April 2006

H. Körner
Affiliation:
Deutsche Forschungs- und Versuchsanstalt für Luft- und Raumfahrt e.V. (DFVLR), Braunschweig and Köln, Germany
E. H. Hirschel
Affiliation:
Deutsche Forschungs- und Versuchsanstalt für Luft- und Raumfahrt e.V. (DFVLR), Braunschweig and Köln, Germany

Abstract

Self-diffusion coefficients were determined experimentally for lateral dispersion of spherical and disk-like particles in linear shear flow of a slurry at very low Reynolds number. Using a concentric-cylinder Couette apparatus, recurrent observations were made of the lateral position of a particular radioactively labelled particle. The self-diffusion coefficient D was calculated by means of random-walk theory, using the ergodic hypothesis. Owing to great experimental difficulties, the calculated values of D are not of high accuracy, but are correct to within a factor of two. In the range 0 < ϕ < 0·2, D/a2ω increases from zero linearly with ϕ up to D/a2ω ≈ 0.02 (where ϕ = volumetric concentration of particles, a = particle radius, ω = mean shear rate of suspending fluid). In the range 0.2 < ϕ < 0.5, the trend of D/a2ω is not clear because of experimental scatter, but in this range D/a2ω ≈ 0·025 to within a factor of two. Within the experimental accuracy, spheres and disks have the same value of D/a2ω.

Type
Research Article
Copyright
© 1977 Cambridge University Press

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