Measurements of the Terminal Velocity of Bubbles Rising in a Chain

Abstract

Measurements were made of the effect of frequency of formation on the velocity of air bubbles rising in a chain through distilled water, lap water, and sugar water. In all cases, increasing the frequency increased the rise velocity for a given bubble size. Measurements made in distilled water showed that the increase of velocity with frequency dropped off with bubble size until it was negligible for the smaller bubbles. It was shown that the variation of bubble velocity with frequency and size can be fairly well correlated with the velocity of rise of solitary bubbles by means of a model based on turbulent wake theory. Tap-water measurements showed the same effect of impurities in the water on the bubble rise velocity as had been observed for solitary bubbles; however, the bubble radius at which the effect became apparent decreased with frequency. Measurements made in sugar water showed that the effect of fluid properties on the rise velocity decreased as frequency increased. At the highest frequencies, no difference could be seen between the distilled water and the sugar water rise velocity curves.