Stratified/slug transition boundary

For the sake of clarity, the focus in Figure 18 is on the interplay and practical relevance of the stability boundaries (ZNS or ZNS) and the L-T laminar/turbulent flow regime transitional line in predicting the stratified-smooth/wavy flow pattern transition. Other transitional boundaries, which confine the stratified-smooth and stratified-wavy zones, are shown in Figure 19. For relatively low gas rates, the stratified-smooth zone is bounded by the slug or bubbly patterns while the stratified-wavy zone, at high gas rates, is bounded by the transition to annular pattern. 

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