Influence of finite-density fluctuations on the development of the Rayleigh–Taylor instability in a porous medium

We numerically simulate the Rayleigh–Taylor convection in a porous medium in the presence of initial density fluctuations at the interface between two fluid layers. We consider miscible fluids: the lower layer is composed of a single-component fluid medium, and the upper layer, of the same medium with an admixture dissolved in it. We study the influence of the density fluctuation amplitude on the onset and the development of convective motion. We find that as the fluctuation amplitude decreases, the convection begins significantly later, the induced convective “fingers” become wider, and the velocity of their motion decreases. We also observe the effect of initial fluctuations during the transition to stochastic flows when the initial quasiperiodic convection structure is broken.