We report on convection near threshold in circular samples of radial aspect ratio $\Gamma =11.5\mathrm{}$ using ethanol-water mixtures with two concentrations $x$, but with the same separation ratio $\Psi \simeq -0.08\mathrm{}$. For $x=0.250\mathrm{}$, convection begins with transients that lead to a time-independent cell-filling state, typically in a day. For $x=0.011\mathrm{}$, there is a range of temperature differences where repeated transients and aperiodically fluctuating localized regions of disordered convection persist for many days. In rare cases these lead to an apparently stable "wall" state of traveling waves surrounding pure conduction.

• Received 29 September 1995

DOI:https://doi.org/10.1103/PhysRevE.53.R2041