Rayleigh–Taylor-Like Instability in Near-Critical Pure Fluids

The hydrodynamic stability of a thermodiffusive iInterface in a near-supercritical fluid is studied. The Navier-Stokes equations written for a van der Waals gas above its critical point are solved by means of a finite volume numerical method. The growth rate of the fluctuations shows that there exists a cutoff wave number beyond which the short wavelengths are stabilized by diffusion. The good agreement between the obtained values and recent theories for miscible fluids confirms that a near-critical fluid subjected to a thermal gradient may develop a gravitational instability for which the density gradient is driven by thermal diffusion and large compressibility