Abstract
The present paper was devoted to improving the understanding and modeling of upward turbulent bubbly flow (TBF) in the large noncircular duct. Recent experiments of the upward TBF in a large vertical square duct showed a significant peak of the axial liquid phase velocity (Wl) near the corner and wall except the pronounced corner and wall peak of the void fraction [1]. However, few observations of such significant velocity peak were reported near the wall in the currently existed circular-pipe database except slightly peak. The paper presents the analysis on the formation of the typical shape of Wl by considering an index to show the shape of velocity profile and the formation condition of the typical M-shape. The index to show the shape of the velocity profile was discussed. It indicates the flow with smaller wall resistance, larger and steeper profile of the void fraction is easier to form M-shaped velocity profile. Besides, it was obtained that for the upward TBF in the large square duct, there may exist two layers with different flow types between the wall and center.
