Churn and Wispy Annular Flow Regimes in Vertical Gas–Liquid Flows

Two-phase flows are extremely complex and, traditionally, attempts have been made to classify the myriad of possible flow configurations into “flow regimes” or “flow patterns”. Classically, vertical two-phase flows have been classified into the regimes of bubbly flow, slug flow, and annular flow. This paper makes an appeal for two other regimes, namely, “churn flow” and “wispy annular flow”, to be given more attention. As shown, these regimes are of considerable technological importance and possess unusual features that justify their separate designation and make them ripe for further study.