Merging of drops to form bamboo waves

Topological transitions in core-annular flow of oil and water are described . Drops of one liquid are suspended in the second liquid and transported th rough a pipeline under a pressure gradient. We examine the merging of an ar ray of drops in this two-fluid flow. Larger drops are found to merge and th e flow undergoes a topological transition to core-annular flow. In core-ann ular flow of two liquids, one liquid lies at the core and the other surroun ds it. For the case of large oil bubbles in water, a steady core-annular fl ow with bamboo waves on the interface is achieved. For the case of large wa ter bubbles in oil, the ensuing core-annular flow has continually breaking waves at the interface. (C) 2001 Elsevier Science Ltd. AII rights reserved.