Particle velocity fluctuations and hydrodynamic self‐diffusion of sedimenting non‐Brownian spheres
作者:
H. Nicolai,
B. Herzhaft,
E. J. Hinch,
L. Oger,
E. Guazzelli,
期刊:
Physics of Fluids
(AIP Available online 1995)
卷期:
Volume 7,
issue 1
页码: 12-23
ISSN:1070-6631
年代: 1995
DOI:10.1063/1.868733
出版商: AIP
数据来源: AIP
摘要:
The motion of non‐Brownian spheres settling in the midst of a suspension of like spheres has been experimentally studied under creeping flow conditions. A few glass spheres, marked with a thin coating of silver, were tracked in a suspension of unmarked glass spheres, made optically transparent by matching the index of refraction of the suspending fluid to that of the glass spheres. Particles were tracked with a real time digital imaging processing system. Particle trajectories were examined in the bulk region of the suspension for particle volume fractions ranging from 0% to 40% in 5% steps. Statistical analyses of local particle velocities yield the mean settling velocity, the RMS of the fluctuations of the vertical and horizontal particle velocity and the particle velocity autocorrelation functions. The long time fluctuating particle motion is demonstrated to be diffusive in nature. Vertical and horizontal correlation times and self‐diffusivities are found as a function of particle volume fraction, and a strongly anisotropic diffusion noted. ©1995 American Institute of Physics.
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