04. Boiling and Multi-Phase Flow

The shapes and terminal velocities of single bubbles rising through a vertical fiber bundle were studied in the surface tension force and the inertial force dominant regime. The liquid phases were glycerol-water solutions and a xanthan gum-water solution which is non-Newtonian fluid in addition to water dealt with in our previous study. Fibers with 2 mm diameter were arranged in bundles of 4 x 4, 6 x 6, and 12 x 12 configurations, with pitches Lp of 18 mm, 12 mm, and 6 mm, respectively. The terminal velocity, lateral movement, and shape of bubbles were obtained from images recorded by using a high-speed camera. The presence of fibers made the terminal velocities enhance with increasing the number of fibers, i.e. decreasing Lp, regardless of liquids. This tendency was remarkable in the cap-bubble regime. Top view images indicate that the velocity increase due to fibers would relate to the large shape deformation of bubbles. The correlation of the drag coefficients developed for water cases including the fiber effects should be modified for accurate evaluation of the terminal velocities of single bubbles in the aqueous solutions.

Gherhardt Ribatski

Prof.