Pattern Selection in Salt Fingers

Abstract

Double-diffusive convection Is the term commonly used to describe what happens in fluids in which two components with different molecular diffusivities contribute in an opposite sense to the vertical density gradient. The term thermo-haline convection was introduced to describe oceanographic systems where the two components are heat and salt. In such systems, convective instabilities occur even though the net density distribution is decreasing upward. Two basic types of flow arise depending on whether the component which is heavy at the top is the one with the higher or lower diffusivity. The “fingers” regime occurs when a layer of warm salty water overlies a colder and fresher water layer. The opposite case (a layer of warm salty water under a colder fresher water layer) is called the thermo-diffusive regime A full description of the instability mechanism in both cases, together with more details about the experiments and simple theoretical models can be found in earlier reviews[1,2,3]