Bubble Formation Due to a Submerged Capillary Tube in Quiescent and Coflowing Streams

Abstract

The case of bubble formation in both quiescent and moving streams due to the injection of a constant gas flow through a small tube is considered. Relationships predicting the expected size and quantity of bubbles generated are proposed. These are compared with measurements taken with stream velocities up to 9 ft/sec, while generating gas bubbles from 40 to 700 microns in diameter. For the case of generation in a quiescent stream the forces due to the virtual mass, surface tension, viscous drag, buoyancy, and the wake formed by the preceding bubble are accounted for. There still remains some question (only partly answered by a comparison with measurements) as to the proper added mass coefficient and the geometry of the bubble previous to detachment, as well as an adequate estimate of the interaction with a preceding bubble’s wake. The proposed model for generation in a moving stream is in good agreement with actual measurements for co-flowing velocities between 1 and 9 fps and capillary tubes in the order of 10−3 cm in dia.