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 bubbles trailed closed, laminar toroidal wakes. For 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 H2 tracer bubbles. Results are presented for R < 150 and 7·4 × 10−4 < M < 850.

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Some anomolous observations of the gas holdup behaviour in binary organic liquid mixtures in a bubble column are reported in this note, to supplement the recently published data(1). The gas holdup was higher for mixtures of organic liquids than for either pure component. It is shown that none of the existing theories fully explains the data.

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A general one-dimensional theory for predicting the average holdup or column concentration in three phase flow is formulated. The analysis takes into account the local relative velocity between the phases, the non-uniform flow and holdup distribution across the column, and the effect of the concentration of the dispersed phase on the relative velocity. The present theory is compared with the previous analyses for two phase flow reported in the literature and it is shown that all of them are special cases of the general theory proposed hme. he problem of two and three phase flows in pipe