Bubble-laden thermals in supersaturated water

Bubble-laden thermals provide a formidable gas transport mechanism responsible, for instance, for the explosive foaming-up process during the beer tapping prank, or the infamous gas eruption of Lake Nyos in 1986. In this work we investigate experimentally the growth and motion of laser-induced turbulent thermals in a carbonated water solution with surfactants. One of the novelties of this study is that we are able to quantify with high temporal resolution the rate at which the gas volume contained in the bubbles grows. After an initial transient stage, the gas bubble and entrained liquid volumes of the thermal both grow as a cubic power of time. The buoyancy generation rate is well explained by the mass transfer scaling expected for individual bubbles. In contrast, the thermal rise velocity does not adhere to any particular scaling law. These facts lie in qualitative agreement with a phenomenological model, based on classical models for turbulent thermals, that takes into account buoyancy generation.We acknowledge the support of the Spanish Ministry of Economy and Competitiveness through grants DPI2017-88201-C3-3-R and DPI2018-102829-REDT, partly funded through European Funds. This work was supported by the Netherlands Center for Multiscale Catalytic Energy Conversion (MCEC), an NWO Gravitation programme funded by the Ministry of Education, Culture and Science of the government of the Netherlands

Some Topics on the Physics of Bubble Dynamics in Beer

Besides being the favorite beverage of a large percentage of the population, a glass or bottle of beer is a test bench for a myriad of phenomena involving mass transfer, bubble-laden flows, natural convection, and many more topics of interest in Physical Chemistry. This paper summarizes some representative physical problems related to bubbles that occur in beer containers, pointing out their practical importance for the industry of beverage processing, as well as their potential connection to other processes occurring in natural sciences. More specifically, this paper describes the physics behind the sudden foam explosion occurring after a beer bottled is tapped on its mouth, gushing, buoyancy-induced motions in beer glasses, and bubble growth in stout beers.We acknowledge the support of the Spanish Ministry of Economy and Competitiveness through grants DPI2014-59292-C3-1-P and DPI2015-71901-REDT, partly funded through European Funds. We are also grateful to Jaume Lluis Tartera, from the beer company Mahou-San Miguel, for pointing out to the authors some very interesting aspects of the role of foam in beer

Shaky life of a water drop in an anise oil-rich environment

This paper is associated with a video winner of a 2018 APS/DFD Milton van Dyke Award for work presented at the DFD Gallery of Fluid Motion. The original video is available online at the Gallery of Fluid Motion, https://doi.org/10.1103/APS.DFD.2018.GFM.V0054This paper is associated with a video winner of a 2018 APS/DFD Milton van Dyke Award for work presented at the DFD Gallery of Fluid Motion.We acknowledge the support of the Spanish FEDER/Ministerio de Ciencia, Innovación y Universidades – Agencia Estatal de Investigación through Grants No. DPI2014-59292-C3-1-P, No. DPI2015-71901-REDT, and No. DPI2017-88201-C3-3-R

Transition to convection in single bubble diffusive growth

We investigate the growth of gas bubbles in a water solution at rest with a supersaturation level that is generally associated with diffusive mass transfer. For CO2 bubbles, it has been previously observed that, after some time of growing in a diffusive regime, a density-driven convective flow enhances the mass transfer rate into the bubble. This is due to the lower density of the gas-depleted liquid which surrounds the bubble. In this work, we report on experiments with different supersaturation values, measuring the time t(conv) it takes for convection to dominate over the diffusion-driven growth. We demonstrate that by considering buoyancy and drag forces on the depleted liquid around the bubble, we can satisfactorily predict the transition time. In fact, our analysis shows that this onset does not only depend on the supersaturation, but also on the absolute pressure, which we corroborate in experiments. Subsequently, we study how the depletion caused by the growth of successive single bubbles influences the onset of convection. Finally, we study the convection onset around diffusively growing nitrogen N-2 bubbles. As N-2 is much less soluble in water, the growth takes much longer. However, after waiting long enough and consistent with our theory, convection still occurs as for any gas-liquid combination, provided that the density of the solution sufficiently changes with the gas concentration