Simultaneous Measurements of Bubble and Liquid Velocities in Two-Phase Bubbly Flow Using Laser Doppler Velocimeter

Abstract

Simultaneous measurements of local velocities of both phases in a two-phase bubbly flow have been successfully made using a laser Doppler velocimeter (LDV). First, an exact theory which forms the basis of the velocity measurement of a large particle, such as bubble, has been derive and its validity has been applied to an air-water vertical bubbly flow. As a result, it has become evident that the measured value of a local slip velocity between bubble and liquid is lower than a terminal velocity of a single bubble rising in still water, and that the slip velocity gradually decreases with an increase in the mean liquid velocity.