Weakly Nonlinear Traveling-Wave Convection

Experimental results are presented for traveling-wave states near the onset of convection in a fluid mixture in a rectangular container. When the Soret-effect-induced stabilization is sufficiently weak, the nonlinear oscillatory states at onset evolve in time from the linear states of the system and remain in a pattern of parallel rolls with a frequency which is always near the Hopf frequency (i.e., $\frac{\Delta f}{f_0}\lesssim 0.15$). However, these states exhibit erratic spatial and temporal behavior which is apparently due to the non-linear coupling of the counterpropagating traveling waves.