Study of a downward bubbly flow in a vertical pipe

This paper reports on an experimental study of downward bubble-diffused concurrent flow in a vertical pipe. Two-phase flow was induced by introducing gas into a liquid with a special mixer which made it possible to obtain a gas-liquid flow with consistent bubble size. Visualization was performed by photography and flow rate was monitored by friction transducers. Shear stress and hydraulic conductivity were determined for various flow rates and Reynolds numbers. It was found that the stabilizing effect of the gas phase is determined by the fact that the flow rate pulsations introduced into the liquid flow have a negative sign; that the flow rate of the liquid near the bubbles, in other words, is lower than the mean flow rate of the liquid. This effect is not seen in ascending flows.