28 



Figure. 18a 



ELLIPSOIDAL BUBBLES 



For larger bubble sizes, the surface forces, which are essential in maintaining the 

 spherical shape of a bubble, become smaller in comparison to the viscous and hydrodynamic 

 forces, and flattening of the bubble occurs. This flattening to approximately an oblate 

 spheroid results in higher drag as compared to a sphere of the same volume. Figure 20 shows 

 the drag curves of ellipsoidal and spherical cap bubbles in terms of the Reynolds number. 

 The estimated extent of the regions of ellipsoidal and spherical cap bubbles is indicated 

 in the figure. It will be observed that the region of ellipsoidal bubbles for the various liquids 



