Air Bubble Entrainment In Free Surface Turbulent 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

A useful source of ideas and information for scientists whose work involves understanding and modelling turbulent flows with free surfaces.

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 ...

This book is a useful source of ideas and information for scientists whose work involves understanding and modelling turbulent flows with free surfaces. It has the following merits: (1) It provides a framework for developing the analysis of this field, which, although important, has received only limited study; (2) It recognizes the importance of the two-phase nature of strongly disturbed free surface flows, with both natural and technological applications; (3) It suggests possible lines of future research (especially experimental) to quantify the characteristics of flow regimes which are mainly known qualitatively at present.

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

This monograph is aimed at the practising hydraulic engineer. Work on it commenced at Professor Naudascher's instigation in 1982. Over the next six years all or some of the authors discussed progress at IAHR sponsored conferences at Esslingen, Melbourne, Lausanne and Beijing. With the authors scattered throughout the world, and all with other responsibilities, progress was bound to be slow. Completion was further delayed by the great increase in published technical literature in this area over the period 1982-1988. This literature continues to expand and with it our understanding of the air water flow phenomena. The monograph must therefore be seen as the authors' views on the state of the art around 1988. More recent references have been included for completeness.This monograph has been a joint effort with most authors making suggestions and contributions to more than one chapter. Nevertheless, the chapter authors are primarily responsible for the material in their chapters.Throughout the monograph symbols are defined when they are fist introduced and a list of symbols is included at the end of each chapter.Many other people have contributed to this monograph, but the authors would particularly like to acknowledge the assistance given by Professor John McNown who has read, commented on and improved the style of the complete monograph.

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

Rivers form one of the lifelines in our society by providing essential services such as availability of fresh water, navigation, energy, ecosystem services, and flood conveyance. Because of this essential role, mankind has interfered continuously in order to benefit most and at the same time avoid adverse consequences such as flood risk and droughts. This has resulted in often highly engineered rivers with a narrow set of functions. In the last decades rivers are increasingly considered in a more holistic manner as a system with a multitude of interdependent processes. River research and engineering has therefore added to the river fundamentals also themes like ecohydraulics, consequences of climate change, and urbanisation. River Flow 2020 contains the contributions presented at the 10th conference on Fluvial Hydraulics, River Flow 2020, organised under the auspices of the Committee on Fluvial Hydraulics of the International Association for Hydro-Environment Engineering and Research (IAHR). What should have been a lively physical gathering of researchers, students and practitioners, was converted into an online event as the COVID-19 pandemic hindered international travelling and large gatherings of people. Nevertheless, the fluvial hydraulics community showed their interest and to be very much alive with a high number of participations for such event. Since its first edition in 2002, in Louvain-la-Neuve, this series of conferences has found a large and loyal audience in the river research and engineering community while being also attractive to the new researchers and young professionals. This is highlighted by the large number of contributions applying for the Coleman award for young researchers, and also by the number of applications and attendants to the Master Classes which are aimed at young researchers and students. River Flow 2020 aims to provide an updated overview of the ongoing research in this wide range of topics, and contains five major themes which are focus of research in the fluvial environment: river fundamentals, the digital river, the healthy river, extreme events and rivers under pressure. Other highlights of River Flow 2020 include the substantial number of interdisciplinary subthemes and sessions of special interest. The contributions will therefore be of interest to academics in hydraulics, hydrology and environmental engineering as well as practitioners that would like to be updated about the newest findings and hot themes in river research and engineering.

This open access book presents a series of complicated hydraulic phenomena and related mechanism of high-speed flows in head-head dam. According to the basic hydraulic theory, detailed experiments and numerical simulations, microscopic scale analysis on cavitation bubbles, air bubbles, turbulent eddy vortices and sand grains are examined systemically. These investigations on microscopic fluid mechanics, including cavitation erosion, aeration protection, air–water flow, energy dissipation and river-bed scouring, allow a deep understanding of hydraulics in high-head dams. This book provides reference for designers and researchers in hydraulic engineering, environment engineering and fluid mechanics.