Liquid film falling around taylor bubbles rising inside tubes slightly inclined from the vertical

Resumo

The present work reports an experimental study of single elongated bubbles rising in water-glycerin mixtures inside vertical and slightly inclined round tubes. The bubble velocities were measured by using a visualization technique with high speed video camera and a pulse-echo ultrasonic technique. The thicknesses of the liquid films falling around the bubbles were also measured by using a pulse-echo ultrasonic technique. Four transducers were mounted at the top of the tube to detect the rising bubble, allowing the determination of the bubble profiles representatives of the central vertical and horizontal planes of the tube. Six inclination angles were studied from the vertical. The experimental results indicated that the bubble velocity increased when the tube inclination increased, for all liquids studied. Additionally, it was observed that, for a given inclination angle, the bubble velocity decreased when liquid viscosity increased. Concerning the liquid film thicknesses, a loss of symmetry in relation to the tube axis was observed, when the bubble moves inside an inclined tube . The bubble was pushed towards the upper wall of the tube by the radial component of the buoyancy force, losing the symmetry in the vertical direction, i.e. the film thickness above the bubble became smaller than that below the bubble.