VORTEX - Grupo de Mecânica dos Fluidos de Escoamentos Complexos


Análise de Estabilidade Hidrodinâmica e Magnética de Leitos Fluidizados, (2004).

Autor: Yuri Dumaresq Sobral

Orientador: Francisco Ricardo Cunha

Resumo
The determination of a consistent set of governing equations for fluidized beds is still an opened question in fluid mechanics of particulate flows. This is due to the fact that there are not enough experimental evidences that allow a definitive identification of the physical mechanisms that take place on the dynamics of fluidized beds. A model that considers the particles as a disperse continuum phase is proposed in this work. Only relevant terms, for those physical mechanisms that are evidenced from observations, are considered. The model for the fluid-particle interaction force is motivated by a theoretical study of the arbitrary motion of an isolated particle. The stability of fluidized beds systems is investigated and the influence of the models for the particle pressure, particle viscosity and fluid-particle interaction force is stablished. The particle pressure, associated to the momentum transfer due to particle fluctuations, shows to be a stabilizing effect, since it reduces the amplification growth rate of small amplitude disturbances. In addition, non- linear effects on the wakes of the particles exert a stabilizing contribution on the bed. An extension of the hydrodynamic model is proposed to investigate the stability of polarized fluidized beds. The presence of a magnetic field favorizes the attenuation of concentration waves along the bed. Finally, the instabilities of fluidized beds are examined under the light of interactions of waves of different wave lengths.

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