Transitions between convective reaction fronts in a Poiseuille flow

Density driven convection changes the speed and shape of autocatalytic reaction-diffusion fronts propagating in liquids. These fronts acquire different symmetries depending on domain size and density gradients. In vertical tubes, the front shape can change from flat to nonaxisymmetric, and then to axisymmetric for larger density gradients. Imposing a Poiseuille flow will affect the transition between the different types of fronts, depending on the strength and the direction of the flow, with the nonaxisymmetric state dissapearing for strong flows. In most circumstances, the speed of the front decreases for fronts propagating against the direction of the Poiseuille flow. However, in some cases an adverse Poiseuille flow increases the front speed. This phenomena takes place near a transition between different types of fronts. Tilting the tube significantly changes the front propagation, increasing to a maximum speed for angles away from the vertical direction. In this paper, we study the combined effects of convection and forced Poiseuille flow in inclined tubes, solving numerically the reaction-diffusion equations coupled to the Navier–Stokes equations.