3-D TURBULENCE STRUCTURE AND PHASE DISTRIBUTION MEASUREMENTS IN BUBBLY 2-PHASE FLOWS

Turbulent bubbly air/water two-phase up and down flows in a circular test section were investigated. Important flow quantities such as local void fraction, liquid velocity and the Reynolds stresses were measured using both single-sensor and three-sensor hot-film anemometer probes. For up flows, it was found that the bubbles tended to migrate toward the wall and thus the void fraction profile showed a distinct peak near the wall. In contrast, for down flows, it was found that the bubbles tended to migrate toward the center of the pipe causing void 'coring'. It was also found that the observed wall peaking and coring phenomena, and thus the radial void distribution in up and down flows, could be predicted by considering the turbulence structure of the continuous phase and lateral lift force acting on the dispersed phase (i. e. the bubbles).