Dimensionless Analysis of the Effects of Junction Angle on the Gas-Liquid Two-Phase Flow Transition and the Scaling Law of the Microbubble Generation Characteristics in Y-Junctions

Abstract

Gas-liquid two-phase flow patterns and gas slug hydrodynamics were experimentally studied in three Y-junctions with different junction angles of 60°, 90° and 120°. Microbubbles were generated in the sodium alginate aqueous solution with the surfactant Tween20. Four main flow patterns were observed, i.e., stratified flow, annular flow, dispersed bubble flow and slug bubble flow. The formation mechanism of the bubble flow was explained by a force analysis, which was based on the dimensionless analysis regarding Capillary number, Weber number and Euler number. The transition criteria of the gas-liquid two-phase flow patterns was set up by these three dimensionless numbers. Additionally, the characteristics of the slug bubble were investigated, which made a scaling criterion for eliminating the influence of the angle factor become possible. A new scaling law (validity range within 2.88 < Re1 < 14.38, 0.0068 < We1 < 0.1723) was proposed to predict the bubble size and it showed a good agreement with the experimental results.