Ultrasound Doppler measurement of air-lift two-phase and particulate three-phase pipe flows

Air-lift two-phase and particulate three-phase flow in a vertical pipe has been measured by the ultrasound Doppler method with the aim of revealing the local transient dynamics of the multiphase fluid to explain the air-lift performance. Changing the gas flow rate and mass loading of solid particles in the liquid phase, we measured the void fraction and liquid flow rate in the slug-flow regime at 55 Hz sampling rate. The echo amplitude profile was analyzed with several space-time filtering algorithms to detect dispersed bubbles and large pipe-occupying bubbles. The Doppler-shift profiles were processed to measure the instantaneous liquid flow rate, which is correlated with the void fraction. From the synchronized measurements, we found that mixing the liquid phase with solid particles reduced the mean axial length of the bubbles and the correlation between the liquid flow rate and the void fraction was reduced because the long slug was destabilized by the particles. Graphical abstract