Rising bubbles and falling drops

Tripathi, M K (2015) Rising bubbles and falling drops. PhD thesis, Indian Institute of Technology Hyderabad.

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Abstract

The fascinating behaviour of bubbles and drops rising or falling under gravity, even without the presence of any impurities or other forces (such as electric, magnetic and marangoni forces), is still a subject of active research. Let alone a uni fied description of the dynamics of bubbles and drops, a full description of a single bubble/drop is out of our reach, as of now. The thin skirted bubbles, for instance, may rise axisymmetrically or may have travelling waves in azimuthal or vertical direction; may or may not remain axisymmetric; may eject satellite bubbles, or they may form wrinkles in their skirt. The length scales may vary across 3 or more orders of magnitude. A rising bubble may change its topology to become a toroidal bubble and become unstable to break into smaller bubbles, which may further break into even smaller bubbles. Bubbles which attain a terminal shape and velocity may change their fi nal behaviour depending on the initial conditions of release. Ellipsoidal bubbles, released axisymmetrically, may often take a zigzag or a spiral path as they rise. On the other hand, drops have a completely di ff erent dynamics. Drops have been studied due to their importance in atomization, rain drop size distribution, emulsi fi cation and many other problems of industrial importance. Apart from the low Reynolds number regime and density ratios close to 1, any literature seldom compares bubbles and drops because of the inherent difference in their dynamics.The reason for this difference has been investigated in

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