Drop Tower Setup to Study the Diffusion-driven Growth of a Foam Ball in Supersaturated Liquids in Microgravity Conditions

Abstract

The diffusion-driven growth of a foam ball is a phenomenon that appears in many manufacturing process as well as in a variety of geological phenomena. Usually these processes are greatly affected by gravity, as foam is much lighter than the surrounding liquid. However, the growth of the foam free of gravity effects is still very relevant, as it is connected to manufacturing in space and to the formation of rocks in meteorites and other small celestial bodies. The aim of this research is to investigate experimentally the growth of a bubble cloud growing in a gas-supersaturated liquid in microgravity conditions. Here, we describe the experiments carried out in the drop tower of the Center of Applied Space Technology and Microgravity (ZARM). In few words, a foam seed is formed with spark-induced cavitation in carbonated water, whose time evolution is recorded with two high-speed cameras. Our preliminary results shed some light on how the size of the foam ball scales with time, in particular at times much longer than what could be studied in normal conditions, i.e. on the surface of the Earth, where the dynamics of the foam is already dominated by gravity after several milliseconds.

Some Topics on the Physics of Bubble Dynamics in Beer

“…The large efficiency of this mechanism in making bubbles grow is further supported by experiments in microgravity, where bubble clouds continue to grow purely by diffusion up to times on the order of several seconds [17] (see Video S4 in Supplemental Materials) . Clearly, these observations reinforce the important role that buoyancy has in mass transfer in carbonated beverages-a topic that will be revisited in Section 4.…”

Machine Learning for 3D Particle Tracking in Granular Gases

“…The application of ML techniques in microgravity research is not restricted to the detection of positions and orientations of floating grains, it may be adapted to the observation of other floating objects in 3D (Vega-Martínez et al 2017). ML-based techniques have also been proposed to reconstruct shapes of free-falling liquid droplets (Zou et al 2018).…”

Growth of a bubble cloud in CO2-saturated water under microgravity

“…The experiment aims at generating a dense bubble cloud in a supersaturated liquid, in our case CO 2 -saturated water, and then observe its evolution using high-speed imaging in microgravity conditions. Figure 1 shows the sketch of the experimental setup, which is based on that described in Vega-Martínez et al 16 . This experiment is fitted into a capsule that is then dropped inside the drop tower of the German Center of Applied Space Technology and Microgravity (ZARM).…”

“…An important aspect is to determine the saturation level of CO 2 of the water in the experiments. Some isolated bubbles appear in almost all the experiments, and we use them to determine the saturation level, ζ , as done in 16 . To this end, we track the evolution of their radii by imaging processing.…”

“…With this motivation in mind, we have carried out experiments in which dense bubble clouds grow in CO 2 -supersaturated water in microgravity conditions. These experiments were performed in the drop tower of the German Center of Applied Space Technology and Microgravity (ZARM) using an improved version of the facility described by Vega-Martínez et al 16 . Besides, inspired by these experiments, we have put together a mathematical model of the growth of a bubble cloud in a supersaturated liquid that is able to explain, albeit in a qualitative fashion, the features of the time evolution of bubble clouds observed in the experiments.…”