4. Annular flow

Reference

Annular flow is one of the typical flow patterns observed in two-phase flows. This flow pattern consists of a fast gas core and a liquid film formed on the channel wall. In a circular pipe, the liquid film exhibits a ring-like shape; hence, it is referred to as annular. Annular flows are formed at high gas flow rates, and the void fraction is therefore typically high, and the liquid film is thin. We consider here co-current upward and counter-current annular flows, which have their practical importance in nuclear and chemical engineering applications.