1. n. [Well Completions, Production Logging]

A multiphase flow regime in near-vertical pipes in which large, irregular slugs of gas move up the center of the pipe, usually carrying droplets of oil or water with them. Most of the remaining oil or water flows up along the pipe walls. The flow is relatively chaotic, producing a frothy mixture. Unlike slug flow, neither phase is continuous. The gas slugs are relatively unstable, and take on large, elongated shapes. Also known as transition flow, this flow is an intermediate flow condition between slug flow and mist flow, and occurs at relatively high gas velocity. As the gas velocity increases, it changes into annular flow.

See: annular flow,  bubble flow,  churn flow,  flow regime,  flow structure,  mist flow,  slug,  slug flow