On bubbles rising through suspensions of solid particles

Abstract

in Wiley InterScience (www.interscience.wiley.com).Individual bubbles rising through suspensions of spherical particles neutrally buoyant in viscous Newtonian liquids are tracked with real time radiography. The effects of the containing cylinder, suspended particle, and bubble sizes are reported for particle volume fractions ranging from 0.20 to 0.50. In the most concentrated suspensions, the effect of the bottom surface is felt by the bubble much farther into the suspension than would be true for a single-phase Newtonian liquid. Corrected for wall effects, the apparent viscosity felt by the bubbles is independent of the relative size of the bubble to the particle over a wide range of parameters, and is approximately linear with the suspended particle volume fraction, in contrast to the exponential dependence derived in conventional rheometry. Finally, in the most concentrated suspensions, the bubble deforms to a prolate spheroidal shape despite the lack of significant inertial effects or a viscoelastic suspending liquid.

Effective drag on spheres immersed in a fluidized bed at minimum fluidization—Influence of bulk solids properties

“…This higher resistance to movement of an immersed sphere appears to be related to the capacity of the bulk solids to migrate inside the emulsion, as indicated by the bulk properties presented in Figure 7B. As reported by other groups, [14,40,41] a FB with highly confined bulk solids (reflected by a void fraction similar to that at repose) will have more restrictions with respect to the recirculation of the bulk solids and will, therefore, exhibit more inertial effects. This is also reflected in the slightly higher values of the Hausner ratio obtained with increased mean particle size of the bulk solids.…”