Environmental Hydraulics Stratified Flows

The present lecture notes cover a first course in th~ most common types of stratified flows encountered in Environ mental Hydraulics. Most of the flows are buoyancy flows, i.e. currents in which gravity acts on small density differences. Part I presents the basic concepts of stagnant, densit- stratified water, and of flowing non-miscible stratified fluids. The similarity to the (presumed) well-known open channel flow, subject to a reduced gravity, is illustrated. Part II treats the miscible density stratified flows. In outlining the governing equations, the strong coupling between the turbulence (the mixing) and the mean flow is emphasized. The presentation and discussions of the basic governing equa tions are followed by illustrative examples. Separate chapters are devoted to Dense Bottom Currents, Free Penetrative Convec tion, Wind-driven Stratified Flow, Horizontal Buoyancy Flow and Vertical jet/plumes. Part III presents some examples of practical problems solved on the basis of knowledge given in the present lecture notes. It is the author's experience that the topics treated in chapter 8 and in the subsequent chapters are especially well suited for self-tuition, followed by a study-circle. ACKNOWLEDGEMENT The author has benefited by the valuable help of his col legues at the Institute of Hydrodynamics and Hydraulic Engin eering, the Technical University of Denmark, especially our librarian Mrs. Kirsten Dj¢rup, our secretary Mrs. Marianne Lewis and our technical draftsman Mrs. Liselotte Norup.

The dynamics of flows in density-stratified fluids has been and remains now an important topic for scientific enquiry. Such flows arise in many contexts, ranging from industrial settings to the oceanic and atmospheric environments. It is the latter topic which is the focus of this book. Both the ocean and atmosphere are characterised by the basic vertical density stratification, and this feature can affect the dynamics on all scales ranging from the micro-scale to the planetary scale. The aim of this book is to provide a “state-of-the-art” account of stratified flows as they are relevant to the ocean and atmosphere with a primary focus on meso-scale phenomena; that is, on phenomena whose time and space scales are such that the density stratification is a dominant effect, so that frictional and diffusive effects on the one hand and the effects of the earth’s rotation on the other hand can be regarded as of less importance. This in turn leads to an emphasis on internal waves.

Triggerd primarily byill effects of polluted air, soil and water resources on living species, public concern for environmental quality has been growing during the past four decades or so. One manifestation of this concern is found in occurrence of public debates as well as in the demand for full environmental impact assessment before a water-resources project is approved. Engineering soundness and economic feasibility are no longer sufficient criteria for construction of hydraulic works. As a result, environmental considerations have become very much a part of hydraulic analyses. In response to growing environmental concerns, the field of hydraulics has expanded and a new branch, called Environmental Hydraulics, has emerged. The focus of this branch is on hydraulic analyses of those environmental issues that are important for protection, restoration, and managementof environmental quality. The motivation for this book grew out of the desire to provide a hydraulic discussion of some of the key environmental issues.It is hoped that the book would serve to stimulate others to write more comprehensive texts on this subject of growing importance.

Triggerd primarily byill effects of polluted air, soil and water resources on living species, public concern for environmental quality has been growing during the past four decades or so. One manifestation of this concern is found in occurrence of public debates as well as in the demand for full environmental impact assessment before a water-resources project is approved. Engineering soundness and economic feasibility are no longer sufficient criteria for construction of hydraulic works. As a result, environmental considerations have become very much a part of hydraulic analyses. In response to growing environmental concerns, the field of hydraulics has expanded and a new branch, called Environmental Hydraulics, has emerged. The focus of this branch is on hydraulic analyses of those environmental issues that are important for protection, restoration, and managementof environmental quality. The motivation for this book grew out of the desire to provide a hydraulic discussion of some of the key environmental issues.It is hoped that the book would serve to stimulate others to write more comprehensive texts on this subject of growing importance.

Sponsored by the Fluids Committee of the Engineering Mechanics Division of ASCE. This report provides environmental engineers with a comprehensive survey of recent developments in the application of fluid mechanics theories to treat environmental problems. Chapters cover principles of fluid mechanics, as well as contemporary applications to environmental problems involving river, lake, coastal, and groundwater areas. Topics include: turbulent diffusion; mixing of a turbulent jet in crossflow -- the advected line puff; multi-phase plumes in uniform, stratified, and flowing environments; turbulent transport processes across natural streams; three-dimensional hydrodynamic and salinity transport modeling in estuaries; fluid flows and reactive chemical transport in variably saturated subsurface media; heat and mass transport in porous media; parameter identification of environmental systems; finite element analysis of stratified lake hydrodynamics; water quality modeling in reservoirs; and linear systems approach to river water quality analysis In addition to providing valuable information to practitioners, this book also serves as a text for an advanced undergraduate or introductory graduate level course.