Dimensional effects in Rayleigh-Taylor mixing.

We study the effects of dimensional confinement on the evolution of incompressible Rayleigh-Taylor mixing both in a bulk flow and in porous media by means of numerical simulations of the transport equations. In both cases, the confinement to two-dimensional flow accelerates the mixing process and increases the speed of the mixing layer. Dimensional confinement also produces stronger correlations between the density and the velocity fields affecting the efficiency of the mass transfer, quantified by the dependence of the Nusselt number on the Rayleigh number. This article is part of the theme issue 'Scaling the turbulence edifice (part 2)'.