Double-Diffusive Christmas Tree

Abstract

Double-and multi-diffusive phenomena occur in fluids containing more than one component contributing to their density (e.g. salt and heat), and exhibit unusually beautiful patterns. Such a pattern in the form of a Chrismas tree is observed when a fluid with stable salinity gradient is heated at a single point. The pattern consists of a primary rising hot plume capped by a vortex dome, a falling downwards annular plume, and a series of layers around and above. A characteristic feature of the layers is the existence of systematic shearing motions and vortices driven by the horizontal shear in the layers, the upward buoyancy flux and the horizontal density gradient. This type of flow can be regarded as a basic individual convective element, and to some extent it plays the same role in the double-diffusive convection problems as the plume in one-component convection problems.