Spherical cap bubbles and skirt formation

Spherical cap bubbles in viscous liquids often develop trailing gas ’’skirts.’’ Fundamental arguments relating to the shape of gas caps, the formation of skirts, their length and thickness are discussed. Experimental results in mineral oil of gas cap indentation, the structure of skirted and nonskirted wakes, the length of skirts, and criteria for skirt formation and skirt instabilities are presented.