Narrow Results

Gas–gas mixing layers are important in many practical applications including transport of pollutants in smoke plumes and air–fuel mixing in combustion. In this paper, mixing layers are studied by conducting direct numerical simulations using a lattice Boltzmann model for binary fluids. The binary fluid model can simulate gases with different molecular weights. In this work, nitrogen–helium and nitrogen–nitrogen mixing layers are studied with different velocities. The computed results are compared with published experimental results and there is agreement between them within 7% for most cases.

We use lattice-Boltzmann simulations to examine late stage spinodal decomposition in binary fluids, showing that the scaling hypothesis for phase ordering does not hold in all cases. We also examine the effects of an applied shear on the coarsening of the spinodal pattern.

It is known that a fluid layer heated from below,³ when the boundaries are poorly conducting, gives rise to long-wavelength instabilities (see e.g. Refs. 5,7). The same effect appears⁸ also in the case of convection in a porous medium.¹⁹ In this work we investigate, analytically and numerically,^6,18 how this effect is influenced by a stabilizing solutal field, both in the case of a fluid layer and in porous media. The solutal field is assigned through fixed concentrations at the boundaries, or more general Robin boundary conditions. The present work concerns a linear stability analysis of the problem and it is part of a larger project including a nonlinear analysis.^9,12,18