Drag coefficients and rotational behavior of spheres descending through liquids along an inclined wall at high Reynolds numbers

作者：Wardhaugh Leigh T; Williams Michael C^*

来源：Physics of Fluids, 2014, 26(3): 035109.

DOI：10.1063/1.4868489

Spherical particles immersed in liquids were observed in their descent along a glass wall inclined at various angles a, over a range of particle-based Reynolds numbers (Re-p) extending to high values (15 < Re-p < 50 000), rarely reported in such flows. Plastic, ceramic, and metal spheres were used, characterized as to surface roughness and their friction coefficients against the glass. Liquids were selected to achieve a viscosity variation by a factor of 300, as well as having widely differing chemical natures. A drag coefficient (C-p) used to correlate sphere velocity data was found to define a near-universal curve C-p (Re-p) over the entire Re-p-range, provided that spheres rolled down the wall without slipping, and here there was no need to accommodate roughness effects of solid-to-solid friction explicitly. This correlation was especially good for Re-p > 10(3). For lower Re-p, deviations appeared in systematic fashion, falling below the universal curve when slip was present. Several unexpected features were observed: (a) a threshold angle, alpha(0), needed before sphere motion could begin; (b) spheres lifting off from the wall at high

• 出版日期2014-3
• 单位CSIRO