caa a22 4500 467891567 CHVBK 20180406152750.0 cr unu---uuuuu 170328e20060801xx s 000 0 eng 10.1007/s10955-006-9078-y doi (NATIONALLICENCE)springer-10.1007/s10955-006-9078-y Hydrodynamic theory for reverse brazil nut segregation and the non-monotonic ascension dynamics [Elektronische Daten] [Meheboob Alam, L. Trujillo, H. Herrmann] Based on the Boltzmann-Enskog kinetic theory, we develop a hydrodynamic theory for the well known (reverse) Brazil nut segregation in a vibrofluidized granular mixture. Under strong shaking conditions, the granular mixture behaves in some ways like a fluid and the kinetic theory constitutive models are appropriate to close the continuum balance equations for mass, momentum and granular energy. Using this analogy with standard fluid mechanics, we have recently suggested a novel mechanism of segregation in granular mixtures based on a competition between buoyancy and geometric forces: the Archimedean buoyancy force, a pseudo-thermal buoyancy force due to the difference between the energies of two granular species, and two geometric forces, one compressive and the other-one tensile in nature, due to the size-difference. For a mixture of perfectly hard-particles with elastic collisions, the pseudo-thermal buoyancy force is zero but the intruder has to overcome the net compressive geometric force to rise. For this case, the geometric force competes with the standard Archimedean buoyancy force to yield a threshold density-ratio, R ρ 1 = ρ l /ρ s < 1, above which the lighter intruder sinks, thereby signalling the onset of the reverse buoyancy effect. For a mixture of dissipative particles, on the other hand, the non-zero pseudo-thermal buoyancy force gives rise to another threshold density-ratio, R ρ 2 (> R ρ 1), above which the intruder rises again. Focussing on the tracer limit of intruders in a dense binary mixture, we study the dynamics of an intruder in a vibrofluidized system, with the effect of the base-plate excitation being taken into account through a 'mean-field' assumption. We find that the rise-time of the intruder could vary nonmonotonically with the density-ratio. For a given size-ratio, there is a threshold density-ratio for the intruder at which it takes the maximum time to rise, and above(/below) which it rises faster, implying that the heavier (and larger) the intruder, the faster it ascends. The peak on the rise-time curve decreases in height and shifts to a lower density-ratio as we increase the pseudo-thermal buoyancy force. The rise (/sink) time diverges near the threshold density-ratio for reverse-segregation. Our theory offers a unified description for the (reverse) Brazil-nut segregation and the nonmonotonic ascension dynamics of Brazil-nuts. Springer Science + Business Media, Inc., 2006 Granular mixture nationallicence Brazil-nut segregation nationallicence Reverse buoyancy nationallicence Nonmonotonic rise velocity nationallicence Alam Meheboob Engineering Mechanics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., 560064, Bangalore, India aut Trujillo L. Centro de Física, Instituto Venezolano de Investigaciones Centíficas, 1029-A, A. P. Caracas, Venezuela aut Herrmann H. Institut für Computer Physik, Pfaffenwaldring 27, Universität Stuttgart, D-70569, Stuttgart, Germany aut Journal of Statistical Physics Kluwer Academic Publishers-Plenum Publishers; http://www.springer-ny.com 124/2-4(2006-08-01), 587-623 0022-4715 124:2-4<587 2006 124 10955 https://doi.org/10.1007/s10955-006-9078-y text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s10955-006-9078-y text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Alam Meheboob Engineering Mechanics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., 560064, Bangalore, India aut NATIONALLICENCE 700 1- Trujillo L. Centro de Física, Instituto Venezolano de Investigaciones Centíficas, 1029-A, A. P. Caracas, Venezuela aut NATIONALLICENCE 700 1- Herrmann H. Institut für Computer Physik, Pfaffenwaldring 27, Universität Stuttgart, D-70569, Stuttgart, Germany aut NATIONALLICENCE 773 0- Journal of Statistical Physics Kluwer Academic Publishers-Plenum Publishers; http://www.springer-ny.com 124/2-4(2006-08-01), 587-623 0022-4715 124:2-4<587 2006 124 10955 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer