Champ instantané́ de la vitesse verticale du liquide. Les cercles matérialisent les bulles.
Because of their low density, the bubbles are set in motion by Archimedes' force, and the ascent of the bubbles drives the liquid. It's a complex system in which bubbles and liquid are coupled, leading to the emergence of collective phenomena and original flow properties. Several parameters influence these mechanisms: the number of bubbles, their size, their speed, the viscosity of the liquid, etc. We study the ascent of a swarm of bubbles of sufficient size to produce large wakes, so that the flow is driven by the interactions between these wakes.
While the equations precisely describing this type of flow are relatively well known, their numerical simulation remains out of reach, due to the wide spectrum of temporal and spatial scales involved. In order to simulate these flows and understand the turbulent transfer and mixing mechanisms involved, we simplify these models by abandoning the precise description of the interfacial dynamics. This allows us to simulate flows with a large number of bubbles and to focus on the interactions between wakes. The main difficulty with this type of calculation arises from the fictitious self-interaction of a bubble with its own wake. We have established a method for correcting this effect and accurately calculating the trajectory of each bubble. Our allocation on the Occigen and Jean Zay machines has enabled us to obtain numerical simulations of turbulence induced by a swarm of bubbles in agreement with experiment, as illustrated above.