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Air bubbles at the surface of water end their life in a particular way: when bursting, they may eject drops of liquid in the surrounding environment. Many uncertainties remain regarding collective effects of bubbles at the water–air interface, despite extensive efforts to describe the bursting mechanisms, motivated by their critical importance in mass transfers between the ocean and the atmosphere in the production of sea spray aerosols. We investigate the effect of surfactant on the collective dynamics and statistics of air bubbles evolving freely at the surface of water, through an experimental set-up controlling the bulk distribution of bubbles with nearly monodisperse millimetric air bubbles. We observe that for low contamination, bubble coalescence is inevitable and leads to a broad surface size distribution. For higher surfactant concentrations, coalescence at the surface is prevented and bubble lifetime is increased, leading to the formation of rafts with a surface size distribution identical to the bulk distribution. This shows that surface contamination has a first-order influence on the transfer function from bulk size distribution to surface size distribution, an intermediate step which needs to be considered when developing sea spray source function as droplet production by bubble bursting depends on the bubble size. We measure the bursting and merging rates of bubbles as a function of contamination through a complementary freely decaying raft experiment. We propose a cellular automaton model that includes the minimal ingredients to reproduce the experimental results in the statistically stationary configuration: production, coalescence and bursting after a finite lifetime.
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Bubble ascent and rupture in mud volcanoes
Large gas bubbles can reach the surface of pools of mud and lava where they burst, often through the formation and expansion of circular holes. Bursting bubbles release volatiles and generate spatter, and hence play a key role in volcanic degassing and volcanic edifice construction. Here, we study the ascent and rupture of bubbles using a combination of field observations at Pâclele Mici (Romania), laboratory experiments with mud from the Imperial Valley (California, USA), numerical simulations and theoretical models. Numerical simulations predict that bubbles ascend through the mud as elliptical caps that develop a dimple at the apex as they impinge on the free surface. We documented the rupture of bubbles in nature and under laboratory conditions using high-speed video. The bursting of mud bubbles starts with the nucleation of multiple holes, which form at a near-constant rate and in quick succession. The quasi-circular holes rapidly grow and coalesce, and the sheet evolves towards a filamentous structure that finally falls back into the mud pool, sometimes breaking up into droplets. The rate of expansion of holes in the sheet can be explained by a generalization of the Taylor–Culick theory, which is shown to hold independent of the fluid rheology.
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- Award ID(s):
- 2116573
- PAR ID:
- 10580412
- Publisher / Repository:
- Royal Society Publishing
- Date Published:
- Journal Name:
- Royal Society Open Science
- Volume:
- 11
- Issue:
- 7
- ISSN:
- 2054-5703
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1098/rsos.231555
