  Shapes and paths of an air bubble rising inside a liquid are investigated
experimentally. About three hundred experiments are conducted in order to
generate a phase plot in the Galilei and Eotvos numbers plane, which separates
distinct regimes in terms of bubble behaviour. A wide range of the Galilei and
Eotvos numbers are obtained by using aqueous glycerol solutions of different
concentrations as the surrounding fluid, and by varying the bubble size. The
dynamics is investigated in terms of shapes, topological changes and
trajectories of the bubbles. Direct numerical simulations are conducted to
study the bubble dynamics, which show excellent agreement with the experiments.
To the best of our knowledge, this is the first time an experimentally obtained
phase plot showing the distinct behaviour of an air bubble rising in a
quiescent medium is reported for such a large range of Galilei and Eotvos
numbers.
