Downward bubbly gas-liquid flow in a vertical pipe

Local characteristics of downward bubbly flow in a 42.3 mm i.d. vertical pipe were investigated. An electrochemical technique was used to measure wall shear stress, local void fraction, liquid velocity, wall shear stress and velocity fluctuations. A gas-liquid mixer was used permitting the change in size of gas bubbles for the same gas and liquid flow rates. Special attention was paid to measurements close to the pipe wall. An increase of wall sheer stress as compared to single-phase turbulent flow was observed. The existence of the single-phase law-of-the-wall was proved for downward flow. A comparison of upward and downward bubbly flow structure was made. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.