open access

https://hdl.handle.net/2115/72144

Oxygen transfer from bubble-plumes

英語

2018-10-31

American Institute of Physics (AIP)

Physics of fluids

30(10)

107104

Air-bubble plumes produced beneath ocean breaking waves have important roles in gas transfer between atmosphere and ocean because the gas within the bubbles, convected by breaking-wave-induced turbulence, is dissolved at a deeper level. In particular, oxygen dissolution supports all biological activities in a marine ecosystem. Oxygen transfer from bubbles to bulk water depends on the dynamics of local bubble flows. As lateral bubble motion associated with vortex wakes generates turbulence in the ambient fluid, depending on the bubble size, the dissolved gas in the plume is transported via complex convection and diffusion processes. Although analytical and empirical models of gas transfer from a small, rigid bubble have been proposed previously, the effects of bubble size on gas concentrations in the turbulence field remain poorly understood. In this study, we examine the explicit effects of bubble size on bubble plume turbulence and the dissolved oxygen (DO) concentration field, and propose a new empirical gas transfer model that is applicable to large deformable bubbles on the basis of experimental imaging analysis. The gas transport process in the plume was identified using bubble turbulence coupled flow computations with the proposed gas source model, which well explained the variation in experimental DO concentration. The proposed transfer velocity model extended the applicable bubble size range and predicted the major features of the increasing oxygen concentration within the plume. We expect these findings to serve as a starting point to improve our understanding of the dynamics of practical bubble plume flows with wider bubble size ranges, as typically formed under breaking waves, and to predict oxygen concentrations in marine environments. (C) 2018 Author(s).

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Creative Commons Attribution 4.0 International

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.The following article appeared in Physics of Fluids 30, 107104 (2018) and may be found at https://doi.org/10.1063/1.5040819.Copyright 2018 Author(s). This article is distributed under a Creative Commons Attribution (CC BY) License.

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