On the interaction between two consecutive elongated bubbles in a verticalpipe

The motion of elongated air bubbles in a vertical pipe filled with water is studied quantitatively using video imaging of the flow and subsequent digi tal image processing of the recorded sequence of images. Experiments are ca rried out to determine the influence of the separation distance between two consecutive bubbles (liquid slug length) upon the behavior of the trailing bubble in vertical slug flow. The details of the trailing bubble accelerat ion and merging process are observed and the instantaneous parameters of th e trailing bubble, such as its shape, velocity, acceleration, etc., are mea sured as a function of the separation distance. The leading bubble is found to be unaffected by the trailing elongated bubble. (C) 2000 Elsevier Scien ce Ltd. All rights reserved.