Influence of dissolved gas concentration on the lifetime of surface bubbles in volatile liquids

TL;DR

The paper addresses how dissolved gas concentration affects the lifetime of surface bubbles in volatile liquids. The authors modulate gas concentration in isopropanol via pressurization/depressurization, quantify oversaturation with $\zeta = (c - c_{sat})/c_{sat}$, and use high-speed imaging to link ruptures to microbubbles nucleating on container walls; film thinning is analyzed through the Taylor-Culick relation $h = \frac{2\sigma}{\rho v^2}$. They find that $t_l$ decreases with increasing $c$ and that rupture is often triggered by microbubbles, with the mean microbubble diameter $\overline{d}$ growing linearly with $c$, leading to a scaling $t_l \sim c^{-3/2}$ (or $t_l \sim (\zeta+1)^{-3/2}$) that holds across container type, pool depth, and bubble size. This scaling sheds light on foam stability and has practical implications for processes and products where surface bubbles in volatile liquids are relevant, such as carbonated beverages.

Abstract

Bubbles at the air-liquid interface are important for many natural and industrial processes. Factors influencing the lifetime of such surface bubbles have been investigated extensively, yet the impact of dissolved gas concentration remains unexplored. Here we investigate how the lifetime of surface bubbles in volatile liquids depends on the dissolved gas concentration. The bubble lifetime is found to decrease with the dissolved gas concentration. Larger microbubbles at increased gas concentration are found to trigger bubble bursting at earlier times. Combined with the thinning rate of the bubble cap thickness, a scaling law of the bubble lifetime is developed. Our findings may provide new insight on bubble and foam stability.

Figures (7)

• Figure 1: The experimental setup to investigate the dependence of surface bubble lifetime on factors such as dissolved gas concentration, container type, pool depth, etc. Bubbles are generated by injecting air at a constant flow rate through a 0.5mm inner diameter needle below the liquid surface. A plastic tube shorter than the liquid depth is put in the liquid pool to fix the position of surface bubbles.
• Figure 2: Isopropanol bubble lifetime $t_l$ at different dissolved gas concentrations represented by the gas oversaturation $\zeta$. Each data point is the average of at least 13 experimental repetitions and the errorbars are the standard deviation
• Figure 3: ($a$) Initial film thickness $h_i$ of isopropanol bubbles at different dissolved gas concentrations represented by the gas oversaturation $\zeta$. The initial film thickness $h_i$ is measured by puncturing the bubble with a needle 0.8-1.3 seconds after it is generated. Each point is the average of 15 bubbles and the errorbars are the standard deviation. The horizontal dashed line is the overall mean $h_i\approx0.93µm$. ($b$) Film thickness at spontaneous rupture $h_r$ for different gas concentrations.
• Figure 4: Snapshots of a rupture event of an isopropanol bubble. The liquid is oversaturated and its dissolved oxygen concentration is $c_\mathrm{o}= 9.33mg/L$. A small particle (the black dot) rises from the bottom to the bubble cap (from $t=0ms$ to 0.24ms), immediately after (0.04ms later), a hole appears and expands at the position of the particle, which later leads to the rupture of the bubble. The scale bar is 2mm.
• Figure 5: Probability of particle-triggered-bursting of isopropanol surface bubbles at different dissolved gas concentrations represented by the oversaturation $\zeta$. 3 to 11 bursting events were counted at each oversaturation, and in total 64 out of 69 bursting events were found to be triggered by a particle, which gives an overall probability of 92.8%.