The shape and the velocity of bubbles in various liquids listed in Table 1 were measured on photographs taken through a stroboscope.
The shape of gas bubbles changed from spherical to ellipsoidal, and then to mushroomlike, as the bubble size increased. The experimental results showed that up to the Reynolds number of 2M^-0.23, the bubble was almost spherical and traveled in a rectilinear path. In the range of 2<ReM^0.23<16.5, ellipsoidal bubbles were formed and as the bubble size increased the shape became flatter. In the range of ReM^0.23>16.5, the bubble was of mushroom shape. These changes in shape are plotted in terms of d/a and ReM^0.23 in Fig. 12, from which experimental equations, Eqs. (12)(15) are derived. These are applicable to bubbles in all solutions except for surface active agent solution. The bubbles in surface active agent solution remained spherical in much bigger size than those in pure water.
Data on the terminal velocity of gas bubbles are shown in Fig. 6. Of spherical and ellipsoidal bubbles, the surface tension and the viscosity were found to be important factors determining the rate of rise. Mushroomlike bubbles rose independently of liquid properties. To correlate the results, dimensionless parameters, C_D, Re and M were employed and experimental equations, Eqs. (9)(11), were obtained for all solutions except for surface active agent solution. These equations agree approximately well with the data of previous investigators summarized in Fig. 16. The presence of certain surface active substances in water served to increase the drag of bubbles, as was made clear by the comparison with the drag of bubbles in pure water.