Double diffusive convection

About: Double diffusive convection is a research topic. Over the lifetime, 1030 publications have been published within this topic receiving 20698 citations.

Buoyancy Effects in Fluids

Abstract: Preface 1. Introduction and preliminaries 2. Linear internal waves 3. Finite amplitude motions in stably stratified fluids 4. Instability and the production of turbulence 5. Turbulent shear flows in a stratified fluid 6. Buoyant convection from isolated sources 7. Convection from heated surfaces 8. Double-diffusive convection 9. Mixing across density interfaces 10. Internal mixing processes Bibliography and author index Recent publications Subject index.

Double-diffusive convection

Abstract: In this paper we present a rather personal view of the important developments in double-diffusive convection, a subject whose evolution has been the result of a close interaction between theoreticians, laboratory experimenters and sea-going oceano-graphers. More recently, applications in astrophysics, engineering and geology have become apparent. In the final section we attempt to draw some general conclusions and suggest that further progress will again depend on a close collaboration between fluid dynamicists and other scientists.

Onset of Thermohaline Convection in a Porous Medium

Abstract: The problem of the onset of convection, induced by buoyancy effects resulting from vertical thermal and solute concentration gradients, in a horizontal layer of a saturated porous medium, is treated by linear perturbation analysis. It is shown that oscillatory instability may be possible when a strongly stabilizing solute gradient is opposed by a destabilizing thermal gradient, but attention is concentrated on monotonic instability. The eigenvalue equation, which involves a thermal Rayleigh number R and an analogous solute Rayleigh number S, is obtained, by a Fourier series method, for a general set of boundary conditions. Numerical solutions are found for some special limiting cases, extending existing results for the thermal problem. When the thermal and solute boundary conditions are formally identical, the net destabilizing effect is expressed by the sum of R and S.

Double-Diffusive Phenomena

Abstract: The study of convective motions produced by unstable density distributions in a fluid is now highly developed. Most attention has been given to the case of a thin horizontal layer of fluid, heated below and cooled above, and results obtained using a combination of Boussinesq theory and laboratory experiments have been success­ fully applied in many contexts (Chandrasekhar 1961, Spiegel 1971). The problem of buoyant convection from isolated sources has also been extensively studied (Turner 1969). Though the effect of adding other processes, such as rotation and magnetic fields, to the buoyant motion has been considered (Spiegel 1972), it has been assumed that the driving density differences are produced by the spatial variations of a single diffusing property (such as heat or a solute). Comparatively recently it has been shown that the simultaneous presence of two components with different diffusivities can lead to a whole range of new phenomena, and these form the subject of the present review. A striking feature of many systems of interest is that instabilities can develop even when the net density decreases upwards. Diffusion, which is generally stabilizing in a fluid containing a single solute, can now act so as to allow the release of the potential energy in the component that is heavy at the top. Much of this work was initiated with an application to the ocean in mind, and because heat and salt (or some other dissolved substance) are then important, the process has been called thermohaline (or thermosolutal) convection. Related effects have now been observed in other contexts, to be described below, and the name double-diffusive convection has been used to encompass this wider range of phenomena. The minimum requirements for the occurrence of double-diffusive convection, in the sense implied here, are the following: (i) The fluid must contain two or more components having different molecular diffusivities. It is the differential diffusion that produces the density differences required to drive the motion. (ii) The components must make opposing contributions to the vertical density gradient. (It is assumed throughout that the fluids are completely miscible, so that surface-tension effects do not arise. Some of the motions produced by the Marangoni

Double-Diffusive Convection due to Crystallization in Magmas

Abstract: An important development in the understanding of the fluid dynamics of convection has been the recognition that heatand mass-transfer processes in multicomponent systems are often fundamentally different to those in the more familiar one-component systems. In a system containing two or more properties that have different molecular diffusivities and opposing effects on the vertical density gradient, a wide range of novel and complex convective phenomena can occur. In the last few years fluid dynamicists and geologists have recognized that such convection, known by the general term of double­ diff usive convection, can occur in magmas and in other fluids of geophysical interest. The implications of this form of convection are far-reaching and are likely to revolutionize our perceptions of many geophysical processes. Theoretical and experimental analyses of double-diffusive convection were first developed in relation to the oceans, specifically with a view to explaining several different kinds of layering (Huppert & Turner 198 1a). It is also apparent that double-diffusive convection is likely to occur in many other systems of geophysical interest. Much attention has been given in particular to the notion that double-diffusive convection can play an important role in the differentiation of magmas. Some of the most