Self-oscillatory convection caused by the Soret effect

A new kind of finite-amplitude convective oscillations in binary mixtures caused by the Soret effect is predicted. Such oscillations can be observed in colloidal solutions of nanoparticles whose diffusion coefficient is about two orders of magnitude less than that for molecules. Due to the small particle mobility the concentration gradient sets in so slowly, that Soret convection starts before this gradient reaches its stationary value. Soon after the onset, however, the convective motion mixes the fluid, that results in rapid damping of the motion. The concentration gradient is then formed again and the process is repeated. A period of these self-sustained oscillations is estimated for real magnetic colloids in the Bénard configuration.