Abstract The present work deals with analysis of instabilities in DCMIX1 ternary systems in the experimental geometry when two liquid layers with different concentrations are superimposed. In multicomponent mixtures, depending on the initial conditions, it is possible to have convective motion even when the top part is less dense than the bottom one. This unstable behavior destroys boundary interfaces unpredictably and affects diffusion processes. Such behavior was examined considering as multicomponent mixture the DCMIX1 ternary system. Due to its three different constituents, the mixture could easily generate two possible types of instability regimes such as: fingers and overstability. Five different compositions have been initially selected, three around the fingers-like type region and two around the overstability region. Experimental results obtained during Sliding Symmetric Tubes (SST) technique based experiments have been compared with the analytical pure diffusion solution and also with a 3D numerical simulation which includes the buoyancy effects. For this purpose, a specific solver in the open source software OpenFOAM has been created. Predicted instabilities agree well with experimental results in most of the cases, confirming the accuracy of the obtained diffusion coefficients.

In the present work, by using a paralelepipedic thermogravitational microcolumn, the temperature gradient influence on the stability of the flow was or has been examined, emphasizing mixtures with negative Soret coefficients. Experiments and numerical analysis were conducted for DCMIX2 Toulene-Methanol binary subsystem. This binary subsystem has a broad range of negative Soret values for low concentrations of Methanol which was analysed. Two different concentrations have been studied in order to confirm existence of temporal stability windows of those mixtures. Experiments were compared with numerical simulations conducted in open source software OpenFOAM, for both cases.