Bubbles in viscous liquids: shapes, wakes and velocities

The shapes and terminal velocities of bubbles rising in viscous liquids have been determined. For Morton numbers ( M ) greater than 4 × 10 −3 the drag coefficient and dimensionless bubble shape are functions only of Reynolds number ( R ). Shape regimes and terminal rise velocities have been correlated. The flow field around a rising bubble was visualized through the hydrogen bubble tracer technique. For M > 4 × 10 −3 and R 110 the wake was open and unsteady. Streamlines for the flow were obtained by raising a ciné camera at the same speed as the bubble and filming the H 2 tracer bubbles. Results are presented for R < 150 and 7·4 × 10 −4 < M < 850.