| We present here the results of the recent experiments on convection in binary fluids close to onset. As a pattern forming system, binary fluid convection provides an opportunity for experimental investigation of the states exhibiting spatio-temporal chaos, as well as the states with interacting planforms with different symmetries. The experiments were conducted in a large aspect ratio circular containers for the case in which the separation ratio, Psi, is negative and convection near onset, for the most part, takes the form of traveling waves. Emphasis is placed on two regimes, one in which the separation ratio is large and negative (i.e., -1.0 < Psi < 0.3), and a second regime in which there are strong non-Boussinesq effects (non-Boussinesq parameter, Q < -2.0). For this range of parameters, both regular and chaotic patterns are observed, consisting of various combinations of traveling waves, standing waves, hexagons, cross rolls, and spirals. Approximate boundaries for transitions between these patterns are established. Results are presented for the competition of hexagons and traveling waves, including the traveling-wave/hexagon front velocity. The properties of cross roll patterns (typically regarded as an instability and not a pattern forming element in stationary patterns) are also studied. |
