Measurement of modulation induced by interaction between bubble motion and liquid-phase motion in the decaying turbulence formed by an oscillating-grid

Abstract

In multiphase flows, dynamical gas–liquid interactions are essential for in-depth understanding of their multi-scale phenomena and complicated structures. The purpose of the present study is to clearly extract the modulation in bubble motion and liquid motion induced by bubble–liquid interaction and to discuss the relations between bubble motion and liquid-phase motion. For this particular purpose, the decaying turbulence formed in a cylindrical acrylic pipe (diameter 149mm, height 600mm) by using an oscillating-grid was employed. Uniform single bubbles were launched from an in-house bubble launching device into the decaying turbulence. By comparing the bubble motion in the stagnant water with that in the oscillating-grid decaying turbulence, the transition of the 2D bubble motion (i.e., zigzagging motion) to 3D motion was enhanced in the latter. In addition, the initial conditions of the bubble motion that was not influenced by the ambient turbulence were carefully confirmed. In the area where the bubble motion started to translate from 2D motion into 3D motion, the modulation of ambient liquid-phase motion was obtained by PIV/LIF measurement. By combining these results, we quantitatively discussed the modulation of the bubble motion and ambient liquid-phase motion and considered the dominant factor for the enhancement to be the bubble–liquid interaction.