Flow characteristics and control of vertical upward gas-liquid two-phase flow through a sudden contraction pipe

The flow characteristics of upward gas-liquid two-phase flow through a vertical sudden contraction pipe is an area that has been less studied experimentally and numerically and that is still little known((1)-(3)). The drag and its reduction for an upward bubbly two-phase flow in a sudden contraction pipe are investigated. Vortices are generated just prior to and after contraction and they significantly affect the flow characteristics. A simple and economical method to control and smoothen the flow is proposed by mounting a small obstacle (ring) upstream the contraction. The effects of ring position, Reynolds number and volumetric gas flow rate are examined and positive results were seen in all flow conditions. Moreover, the pressure fluctuation phenomenon and its control downstream the contraction was considered.