Air Bubble Entrainment In Free Surface Turbulent Shear Flows

This book develops an analysis of the air entrainment processes in free-surface flows. These flows are investigated as homogeneous mixtures with variable density. Several types of air-water free-surface flows are studied: plunging jet flows, open channel flows, and turbulent water jets discharging into air. Experimental observations reported by the author confirm the concept that the air-water mixture behaves as a homogeneous compressible fluid in each case. This book will be of great interest to professionals working in many fields of engineering: chemical, civil, environmental, mechanical, mining, metallurgy, and nuclear. Covers new information on the air-water flow field: air bubble distributions, air-water velocity profiles, air bubble sizes and bubble-turbulence interactions Features new analysis is developed for each flow configuration and compared successfully with model and prototype data Includes over 372 references and more than 170 figures with over 60 photographs Presents useful information for design engineers and research-and-development scientists who require a better understanding of the fluid mechanics of air-water flows

Strong turbulence near an air-water interface, characterized by large Froude (Fr) and Weber number (We), leads to significant interactions and exchanges between gas and liquid, resulting in measurable air entrainment. Air entrainment influences a number of physical processes in the nature, including air-sea gas transfer, production of the sea-salt aerosol and scavenging of biological surfactant. The key factor in controlling these processes is the size distribution of entrained bubbles. However, the underlying mechanisms/physics of air entrainment driven by free-surface turbulence (FST) and the resulted bubble size distribution still remain unclear. Therefore, detailed studies on air entrainment in strong free-surface turbulence (SFST) are of fundamental scientific interest. With recent interest in modeling the white bubbly water in ship wakes, these studies are also of practical importance to the design and analysis of modern surface vessels. In this thesis, we perform both theoretical and numerical studies on air entrainment and bubble size distribution in SFST at large Fr and We. The thesis work 1) characterizes the unique turbulence characteristics of SFST; 2) quantifies the entrainment volume and the corresponding size distribution of SFST air entrainment; 3) elucidates the mechanisms/physics of the bubble size distribution of SFST entrainment; 4) provides useful insight and guidance to the development of sub-grid air entrainment models ...

Develops a physical theory from the mass of experimental results, with revisions to reflect advances of recent years.

Environmental Fluid Mechanics (EFM) studies the motion of air and water at several different scales, the fate and transport of species carried along by these fluids, and the interactions among those flows and geological, biological, and engineered systems. EFM emerged some decades ago as a response to the need for tools to study problems of flow and transport in rivers, estuaries, lakes, groundwater and the atmosphere; it is a topic of increasing importance for decision makers, engineers, and researchers alike. The second edition of the successful textbook "Fluid Mechanics of Environmental Interfaces" is still aimed at providing a comprehensive overview of fluid mechanical processes occurring at the different interfaces existing in the realm of EFM, such as the air-water interface, the air-land interface, the water-sediment interface, the surface water-groundwater interface, the water-vegetation interface, and the water-biological systems interface. Across any of these interfaces mass, momentum, and heat are exchanged through different fluid mechanical processes over various spatial and temporal scales. In this second edition, the unique feature of this book, considering all the topics from the point of view of the concept of environmental interface, was maintained while the chapters were updated and five new chapters have been added to significantly enlarge the coverage of the subject area. The book starts with a chapter introducing the concept of EFM and its scope, scales, processes and systems. Then, the book is structured in three parts with fifteen chapters. Part one, which is composed of four chapters, covers the processes occurring at the interfaces between the atmosphere and the surface of the land and the seas, including the transport of dust and the dispersion of passive substances within the atmosphere. Part two deals in five chapters with the fluid mechanics at the air-water interface at small scales and sediment-water interface, including the advective diffusion of air bubbles, the hyporheic exchange and the tidal bores. Finally, part three discusses in six chapters the processes at the interfaces between fluids and biotic systems, such as transport processes in the soil-vegetation-lower atmosphere system, turbulence and wind above and within the forest canopy, flow and mass transport in vegetated open channels, transport processes to and from benthic plants and animals and coupling between interacting environmental interfaces. Each chapter has an educational part, which is structured in four sections: a synopsis of the chapter, a list of keywords that the reader should have encountered in the chapter, a list of questions and a list of unsolved problems related to the topics covered by the chapter. The book will be of interest to graduate students and researchers in environmental sciences, civil engineering and environmental engineering, (geo)physics, atmospheric science, meteorology, limnology, oceanography, and applied mathematics.

This book comprises the papers of the International Conference on Hydraulics of Dams and Rivers Structures, held in Tehran, 26-28 April 2004. The topics covered include air-water flows, intakes and outlets, hydrodynamic forces, energy dissipators, stepped spillways, scouring and sedimentation around structures, numerical approaches in river hydrody

An environmental interface is defined as a surface between two abiotic or biotic systems, in relative motion and exchanging mass, heat and momentum through biophysical and/or chemical processes. These processes fluctuate temporally and spatially. The book first treats exchange processes occurring at the interfaces between atmosphere and the surface of the sea, and atmosphere and land surface. These exchanges include the effect of vegetation, transport of dust and dispersion of passive substances within the atmosphere. Processes at the environmental interfaces of freshwater, such as gas-transfer at free-surfaces of rivers, advective diffusion of air bubbles in turbulent water flows and boundary-layers phenomena in vegetated open channels are also described. Finally, the book deals with the phenomena that affect transport of material to and from the surface of an organism, including molecular and turbulent diffusion. The relevant issues related to mass transfer to and from benthic plants and animals are further considered in detail. The book will be of interest to graduate students and researchers in environmental sciences, civil engineering and environmental engineering, (geo)physics and applied mathematics.

Comprising the Proceedings of the International Workshop on State-of-the-Art Hydraulic Engineering held in Bari, Italy on 16-19 February 2004, this volume presents an in-depth investigation of the energy loss of skimming flows under a range of discharges, step and dam heights, and channel slopes. Including a wealth of information, the volume is div