Chemical control of hydrodynamic instabilities

Chemical reactions can actively influence, suppress or trigger hydrodynamic instabilities when they change a physical property of the fluid (like its density, viscosity or surface tension). We investigate both experimentally and theoretically the various reaction-diffusion-convection dynamics induced by this interplay between chemical reactions and flows (chemo-hydrodynamics). The objective is to build up general theories of chemo-hydrodynamic pattern selection and devise strategies for chemical control of hydrodynamic instabilities.

Precipitation patterns in flow conditions

When the reactant of a precipitation reaction is injected into another one at a given flow rate in a confined geometry, a wealth of different precipitation patterns can be observed. Our objective is to analyze the effect of changes in the flow rate and concentrations on the properties of the various solid patterns obtained.

Influence of chemical reactions on CO2 sequestration

The dissolution of CO2 into saline aquifers can lead to a buoyantly unstable stratification of denser CO2-enriched brine on top of less dense pure brine, giving rise to fingers rich in CO2 sinking in the host phase. This convective dissolution is favorable to the sequestration of CO2 as it can significantly enhance the dissolution rate of CO2 into the brine, reducing mixing times from thousands to hundreds of years. Our objective is to analyze the influence of chemical reactions on this convective dissolution by combined experimental and theoretical approaches.

Buoyancy-driven instabilities in reactive systems

The interface between two miscible or partially miscible fluids can become unstable because of density differences like in the Rayleigh-Taylor instability developing when a denser fluid overlies a less dense one in the gravity field. Similarly, differential diffusion processes can trigger convective instabilities of miscible interfaces because of the presence of different solutes impacting the density that have different diffusion coefficients. We study by combined experiments and theoretical approaches, the properties of the related convective mixing in two-layer systems both with or without reactions.

Viscous fingering in non ideal and reactive systems

Viscous fingering is a hydrodynamic instability developing in porous media when a fluid of lower viscosity displaces another more viscous one. The interface between the two fluids then deforms into fingers growing in time. Such a fingering instability is detrimental to fluid displacements in oil recovery techniques, contaminant transport in aquifers, in packed bed reactors, and in chromatographic separation techniques. Our goal is to investigate theoretically the influence of viscous fingering on the spreading of viscous samples in the presence of non ideal mixing or chemical reactions.

Convective processes during sea ice growth

As sea ice grows from sea water, the salt dissolved in the liquid phase is rejected from the solid phase. There is current interest to understand the transport processes at the origin of this expulsion of brine out of the sea ice due to their impact on global climate processes. Highly saline brine sinking from sea ice is indeed a driver of global thermohaline circulation whilst convective movements of brine within the ice also influence the movement of gases and nutrients, which affect the Arctic ecosystem. Our objective is to analyze and quantify these convective movements within and below the ice by combined experimental and numerical techniques.

Pattern formation in reaction-diffusion systems

Physico-chemical systems driven far from equilibrium by mass or energy fluxes may develop space or time symmetry breaking bifurcations that lead to time dependent oscillations or space periodic dissipative structures. We investigate theoretically the conditions of appearance of such symmetry breaking instabilities as well as the resulting nonlinear spatio-temporal dynamics. Our results encompass pattern selection theories of 2D and 3D Turing patterns and an analysis of the dynamics resulting from the coupling between Turing and Hopf instabilities. Our current interest lies in the analysis of spatio-temporal dynamics around reaction-diffusion fronts in presence of reactant concentration gradients or radial injection.