3D measurement of interfacial mass transfer of isolated millimetric bubbles in turbulence: Multi-view SI-VILF technique and simultaneous reconstruction of deforming bubble interface and surrounding concentration field

Abstract

To deepen the understanding of the fundamentals of gas dissolution or absorption within turbulent bubbly flows, experiments of interfacial mass transfer should be performed on isolated bubbles in turbulence, while it remains pending for decades. In this paper, we propose a novel idea for indirectly determining the mass transfer coefficient $k_L$based on the law of conservation of mass, avoiding the challenging task of resolving the thin boundary layer at the bubble interface. Based on this idea, the multi-view SI-VLIF technique is developed for 3D measurement of the dissolution of single finite-size oxygen bubbles in turbulent environments. To handle the problem of sparse-view limited-angle imaging, improved 3D reconstruction approaches for the quantities to be measured are developed. The reconstruction qualities are evaluated utilizing synthetic and simulation datasets, and the overall uncertainty in quantifying the $k_L$ is approximately 7%. Lastly, experiments on the oxygen dissolution of millimetric bubbles in quiescent liquid and nearly homogeneous isotropic turbulence are conducted to demonstrate the novel measuring technique. To our knowledge, this is the first time that the 3D mass transfer processes around a deforming bubble rising in turbulent environments are revealed.