THE DEFORMATION OF BUBBLES AND DROPS IN IMMISCIBLE FLUIDS

We consider the uniform motion of a drop of one fluid moving in anothe r immiscible, unbounded, fluid. We examine the condition of normal str ess balance across the interface. Consistent application of this condi tion to linear order in the velocity requires the introduction of a ne w parameter, Delta, which takes into account deformations of the drop from a spherical shape. Imposing a condition for the critical size of these deformations allows us to predict the maximum size of the drop f or a given terminal velocity. For the case of raindrops this gives a m aximum size of approximately 2 millimeters.