Laminar buoyancy - induced flows and transport processes in stratified media

Abstract

Buoyancy?induced flows in a density?stratified environment occur in a wide variety of engineering systems and in nature. Some of these are crystal growth processes, solar ponds, deep ocean power modules, environmental chambers and electronic cooling. In such systems, there is a need to understand and predict the complex interaction between fluid flow and heat and mass transfer. In this thesis computational studies of such complex flows have been undertaken. Chapter 1 introduces the subject and highlights a number of applications in different branches of science and technology. In Chapter 2, relevant literature is cited. Flows are classified according to the orientation of motion?causing potential with respect to gravity. The problems that need our understanding are identified. In Chapter 3, buoyancy?induced flows due to the simultaneous heat and mass transfer in a thermally stratified medium are considered. It is found that boundary?layer flows in highly stratified media are possible if the buoyancy due to mass diffusion is strong. The physical mechanisms of instabilities are identified. Multicomponent plumes in a thermally stratified medium are discussed in Chapter 4. The complex interaction among the buoyancy and other transport properties is presented. An explicit finite?difference scheme is used for solving the governing equations in the above problems. In Chapter 5, natural convection flows adjacent to a vertical surface in a medium of high thermal stratification are considered. Most of the flows are recirculating and require the solution of full Navier–Stokes and energy equations. An Alternating Direction Implicit (ADI) scheme is employed to solve the vorticity transport and energy equations. The results obtained are shown to agree well with the available experimental data in literature. Time?dependent flow behaviour and heat?transfer rates are obtained. Recirculating flows in a horizontal cavity with ambient thermal stratification are presented in Chapter 6. Transient flows are numerically simulated.