Fluctuations, stratification and stability in a liquid fluidized bed at low Reynolds number

• Published in: Journal of physics. Condensed matter Vol. 16; no. 38; pp. S4219 - S4230
• Main Authors: Segrè, P N, McClymer, J P
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Bristol IOP Publishing 29.09.2004; Institute of Physics
• Subjects: Exact sciences and technology; Physics; Multiphase system; Particle size; Fluctuations; Quantity ratio; Fluidized beds; Reynolds number
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/16/38/034

The sedimentation dynamics of extremely low polydispersity, non-colloidal, particles are studied in a liquid fluidized bed at low Reynolds number, Re much less than 1. When fluidized, the system reaches a steady state, defined where the local average volume fraction does not vary in time. In the steady state, the velocity fluctuations and the particle concentrations are found to strongly depend on height in the particle column. Using our results, we test a recently developed stability model (Segre 2002 Phys. Rev. Lett. 89 254503) for steady state sedimentation. The model describes the data well, and shows that in the steady state there is a balancing of particle fluxes due to the fluctuations and the concentration gradient. Some results are also presented for the dependence of the concentration gradient in fluidized beds on particle size; the gradients become smaller as the particles become larger and fewer in number.