Double-diffusive instability in free diffusing layers: a general formulation

The onset of convection induced by concentration gradients, in a horizontal layer of a multi-component fluid, is studied by means of linear stability analysis. A quasi-stationary approximation is used to obtain information about the stability of isothermal multi-component boundaries. A Fourier method has been applied to derive a general equation including both interfacial tension and buoyancy Forces. Such equation is split into the product of two independent factors. Each term is studied to analyse the limit cases: absence of interfacial tension or absence of gravity. The results are also compared with the sufficient conditions used in experiments of mutual diffusion. It is shown that in gaseous multi-component, the stable oscillatory motions are possible. (C) 2000 Elsevier Science B.V. All rights reserved.