Dynamics of bubble swarms in pipe flows at high Reynolds numbers

Two-phase flows in pipes are paramount in several industries, including oil and gas, chemical processing, and nuclear engineering, where efficient transport and mixing of multiphase fluids are critical. For this reason, they have been widely studied across many bubbly regimes and void fraction profiles (e.g., core peaking, edge peaking…) in extensive parameter space. However, many questions remain unanswered, and it remains challenging to establish links with fundamental knowledge either of isolated bubbles in turbulence or of swarms of bubbles at low Reynolds numbers.

We study bubble dynamics in turbulent pipe flows at various bubbly regimes using high-resolution high-speed imaging. Upward, downward, and horizontal configurations and the role of different means of injections are considered. The Reynolds number varies from 5000 to 150 000 and the void fraction from a fraction of a percent to a few percents. Image processing tools and particle tracking velocimetry were used to characterize the size and shape distribution of the bubbles, and the bubble dynamics, and draw quantitative regime maps. We employed particle tracking velocimetry to study the dynamics of the dispersed phase. Additionally, qualitative work is attempted on tumbling and break-up.