Experimental study of single Taylor bubbles rising in vertical and slightly deviated circular tubes

This paper reports an experimental study of single Taylor bubbles rising in stagnant water-glycerin mixtures inside slightly deviated cylindrical tubes. The inclination angles studied were 0 degrees, 2.5 degrees, 5 degrees, 7.5 degrees, 10 degrees and 15 degrees from the vertical. The rise bubble velocity and the shape of the bubbles at two vertical orthogonal planes that intersect at the tube axis were measured by using a pulse-echo ultrasonic technique. Thus, the liquid films draining at the top, bottom and lateral sides of the bubbles were observed. The experimental results indicated that for all liquid mixtures studied, the bubble velocity increased when the inclination angle was increased, and that the bubble velocity was independent of the bubble length. The influence of liquid properties and of tube diameter on the bubble movement and shape were evaluated for deviated angles ranging from 0 degrees to 15 degrees. Different correlations to predict the drift velocity of Taylor bubbles rising in inclined tubes were tested for this particular range of inclination.