Fluid dynamics of double diffusive systems

Abstract

A study of mixing processes in doubly diffusive systems is being conducted. Continuous gradients of two diffusing components (heat and salinity in our case) are being used as initial conditions, and forcing is introduced by lateral heating and surface shear. The goals of the proposed work include: (1) quantification of the effects of finite amplitude disturbances on stable, double diffusive systems, particularly with respect to lateral heating, (2) development of an improved understanding of the physical phenomena present in wind-driven shear flows in double diffusive stratified environments, (3) increasing our knowledge-base on turbulent flow in stratified environments and how to represent it, and (4) formulation of a numerical code for such flows. The work is being carried out in an experimental facility which is located in the Stanford Environmental Fluid Mechanics Laboratory, and on laboratory minicomputers and CRAY computers. In particular, our overall goals are as follows: (1) develop more general stability and scaling criteria for the destabilization of doubly-stratified systems; (2) further study the variation of flow structure and scale with Rayleigh ratio and lateral heating ratio; (3) further delineate the mechanisms governing convective layer formation and merging; (4) study the mixing processes within the convective layers and across interfaces, and estimate the heat and mass fluxes in such a system; (5) quantify the effects of turbulence and coherent structures (due to a wind-driven surface shear) on a doubly stratified system; and (6) study the interaction between surface shear and side-wall heating destabilization mechanisms. 5 refs.