Numerical analysis of binary fluid convection in extended systems

Several aspects of the dynamics of convecting binary mixtures in large aspect ratio containers are analysed using high resolution numerical tools based on spectral methods. For two binary mixtures with separation ratio S = −0.127 and S = −0.021, we compute the Eckhaus stability boundaries of the spatially uniform travelling wave states arising in the primary subcritical bifurcation. The dynamics triggered by Eckhaus instability is discussed for the S = −0.127 mixture. Additionally, for the S = −0.021 mixture, we obtain the complex small-amplitude states observed in experiments for mixtures with a separation ratio very close to zero for the first time with DNS of the full convection equations.