Void fraction effect on bubble deformation of turbulent bubbly flow in a large square duct

For the bubbly flow, the bubble deformation and size are of great importance to calculate the drag and lift forces, which are the key terms to the two-fluid model. Currently, the bubble deformation was mainly considered based on the correlation obtained from the single bubble or droplet experiments. However, for the bubbly flow, the existence of the many bubbles may also affect the bubble deformation. In the present paper, it was regarded that the bubble deformation for the bubbly flow could be statistically treated by the Sauter mean diameter and the chord length measured by a four-sensor optical probe simultaneously. Based on the experimental measurement of the upward turbulent bubbly flow in a large square duct, the statistical bubble deformation was analyzed and the void fraction effect was shown. In addition, the new correlation for the statistical bubble deformation was proposed by the bubble size and the local void fraction, and then validated by the latest experimental data. (author)