Dynamics of a buoyancy-reversing reactive thermal: a laboratory model for oceanic CO₂ injection

Oceanic CO₂ storage involves capturing CO₂ at the source, liquefying it, and dissolving it into the deep ocean. One strategy is to inject a jet of liquid CO₂ from a moving ship to optimize dispersion. Liquid CO₂ is less dense than seawater down to ~2500 m. Yet below ~400 m, CO₂ can react with water to form a solid hydrate that is denser than seawater. The resulting flow thus initially rises, reacts, and then sinks—a reactive fountain flow involving variable buoyancy, turbulent mixing, and a chemical reaction leading to buoyancy inversion. We explore this rich fluid dynamics problem through a model laboratory experiment reproducing the key ingredients, with the aim of understanding the underlying physics and ultimately contributing to the optimization of the industrial process.

A given mass of dense limestone particles is instantaneously released into an acidic medium, triggering a chemical reaction that generates buoyant CO₂ gas bubbles. By varying the particle size, injected mass, and ambient pH, we observe distinct dynamical regimes of this reactive thermal. We will present our systematic experimental exploration and an extension of the classical Morton et al. (1956) model, incorporating chemical reactions and time-evolving buoyancy.