The lateral migration of relative large bubble in simple shear flow in water

The lateral migration of relative large bubble in shear flow was essential for two phase flow modeling when relative large bubble was presented. To better understand the lift force for relative large bubble, the single air bubble motions with diameter ranged from 10 mm to 20 mm in shear flow in water were captured by high speed camera. The linear shear flow with low turbulence intensity was achieved by curved screen. The bubbles were collected in an inverted semi-spherical cup and released by rotating the cup. The lateral migration velocity and quasi-steady lift force were obtained by linear fitting of bubble trajectories. Reproducible results were obtained by measurements of many bubbles. The results showed that bubble shape parameters, rising velocity and drag force were stayed at same level in shear flow as in still water. The relative large bubble migrated to left side and the lift force was negative. A critical bubble diameter of 15 mm was observed which was near the boundary between oblate bubble and spherical cap bubble. When the bubble equivalent diameter was lower than the critical value, the lift coefficient was decreasing with the increasing of shear stress magnitude. When the bubble diameter was larger than the critical diameter, the lift coefficient was monotonically decreased with the bubble equivalent diameter and the shear stress magnitude had no effect in the present experiment condition. The comparison with existing study revealed that the present lift correlations were not able to predict the values and new models were needed.