Hiroaki Kutsuna

Two-phase flow in an annulus with a rotating inner cylinder (flow pattern in bubbly flow region)

Abstract The two-phase flow pattern in a concentric annulus with a rotating inner cylinder have been investigated experimentally. The observed flow patterns were dispersed bubbly, ring-form, single-spiral, double-spiral, triple-spiral flows and transition regions. When the rotational speed was at a relatively low level, the buoyancy effect of bubbles dominated the flow field and a dispersed bubbly flow was formed. On the other hand, when the rotational speed was at a high level, the vortex motion induced by the rotation dominated the flow field and ring-form and spiral flows were formed.

Bubble and Particle Behavior in Taylor- and Spiral-Vortex Flows

The behavior of the bubble and particle in the Taylor-vortex flow was investigated experimentally by using a concentric annulus with a rotating inner cylinder. The flow visualizations by using the tracers indicated that the bubble-ring was located in the out-flow region of the Taylor-vortex close to the inner cylinder, which was also confirmed by the void fraction measurement. The time-averaged radial positions of the particles depended clearly on the specific gravity, and lighter particle was located toward the inner cylinder. The drift velocity of the bubble and particles relative to the volumetric flux decreased with the increase in the Taylor number and became nearly zero or slightly less than zero beyond the certain Taylor number, where the bubble and particles were trapped in the vortex motion. This threshold Taylor number was a decreasing function of the specific gravity of the particles.