Binary-fluid-mixture convection with low-frequency modulated heating

Abstract

The response behavior of binary fluid convection to low-frequency temporal modulation of the heating is studied for the case of a negative Soret coupling between temperature and concentration gradients. Numerical simulations using a finite difference method are carried out for ethanol-water mixtures subject to realistic boundary conditions. We study in particular the response when the Rayleigh number periodically drops below the saddle node in the bifurcation diagram of convective solutions under stationary heating, i.e., into a regime where convection would die out in the absence of modulation. Quasiperiodic traveling waves, several different periodic traveling waves, and synchronously modulated patterns with fixed spatial phase are found as stable solutions depending on parameters. The symmetry properties of the different periodic traveling waves are discussed. Anomalous variations of the mixing behavior relative to advection are observed and explained. Lateral and temporal Fourier decompositions are used together with other diagnostic tools to analyze the complex bifurcation and spatiotemporal properties that are caused by the interplay of modulated heating, nonlinear advection, Soret induced gradients, and mixing of the fluid.