Measurement of interfacial parameters of single Taylor bubbles rising in closed vertical and slightly inclined tubes using ultrasonic and visualization techniques

Resumo

The present work reports an experimental study of single Taylor bubbles rising in water-glycerin mixtures in vertical and slightly inclined tubes filled partially with the liquid mixtures to leave an air pocket at the top end. A Taylor bubble was formed by the inversion of the tube. The velocities and lengths of the rising bubbles were measured by using a pulse-echo ultrasonic technique and a high speed video camera. The bubble profiles and the  thicknesses of the liquid films around the bubbles were measured by the ultrasonic technique. The inclination angles studied were 0^o, 2.5^o, 5^o, 7.5^o, 10^o and 15^o from the vertical position. It was observed, for all liquids studied, that the bubble velocity decreased and the film thickness increased with increasing viscosity. Furthermore, the bubble velocity increased with increasing inclination angle and the influence of the inclination angle on velocity tends to decrease when the liquid viscosity increases. The measurements also indicated that for lower viscosity liquids, the inclination angle has no influence on the length of bubbles generated from the same air volume. However, for higher viscosity liquids, it was observed a tendency of the bubble length to decrease when the inclination angle increases.