The detection and dimension of bubble entrainment and comminution

Data on bubble entrainment and comminution are gathered in three experiments, involving the breakup of a disk of air trapped between two plates, and bubble cloud generation under a waterfall, and a plunging jet. In the second two cases, an automated acoustic system for characterizing the entrainment is employed. The data sets are compared with an existing theory for bubble fragmentation, in which a key parameter is the number of spatial dimensions associated with the insertion of randomly positioned planes which are used to divide up the bubble. While an appropriate best-fit theoretical curve can be obtained for the bubble population histograms generated by air disk comminution, waterfalls and plunging jets produce multimodal distributions which the theory cannot model. The differing roles of shape oscillations and surface waves in bubble fragmentation, and the issues involved with incorporating these into the model, are examined.