Article: Slug flow
Slug flow is a two-phase (gas-liquid) flow. The primary characteristic of slug flow is its inherent intermittence. An observer looking at a fixed position along the axis would see the passage of a sequence of slugs of liquid containing dispersed bubbles, each looking somewhat like a length of bubbly pipe flow, alternating with sections of separated flow within long bubbles. The flow is unsteady, even when the flow rates of gas and liquid are kept constant at the pipe inlet.