Alessandro COMOLLI

Flow control of A+B→C and autocatalytic fronts in confined geometries

  • Supervisor: Anne De Wit & Fabian Brau
  • Research center: Unité de recherche en Chimie physique et Biologie théorique
  • Research start date: 01.01.2021


Recent experiments have shown that precipitation reactions in a radial flow give rise, for example, to a large variety of self-assembled structures, to thermodynamically unstable crystalline forms, to compositions different from those obtained in homogeneous systems and to polymorph selection. In these experiments, a solution of reactant A is injected radially into a solution of reactant B confined in a reactor (Hele-Shaw cell). These systems belong to the general class of A+B→C fronts, where A and B are two distinct miscible reactant species, originally spatially separated, that meet through molecular diffusion and advection to react and produce C. According to the nature of the reactants, such fronts can describe a wide range of different phenomena, for example, in combustion, atmospheric chemistry, and ecological problems. These recent experimental results, together with the genericity of the class of reaction fronts they belong to, highlight the importance of radial transport in reactive systems and the crucial need to understand their dynamics. However, there is no adequate theory to describe these fronts subjected to radial advection. Indeed, the current theories are valid for 1D rectilinear and radial geometries whereas the injection between the two plates of the reactor induces inevitably a Poiseuille profile for the velocity field making de facto the problem at least bidimensional. In this proposal, we aim instead to fill important gaps between the
current theoretical results obtained for simple 1D cases and a more complete description where the governing reaction-diffusion-convection equations must be solved numerically. To do so, we propose a theoretical framework to study the impact of non-uniform velocity fields on the dynamics of A+B→C reaction fronts under passive advection to describe experiments at low concentrations and flow rates. The emergence of transverse instabilities will be studied in the same framework by considering autocatalytic fronts.