Download or read book Factors Affecting Air Entrainment of Hydraulic Jumps Within Closed Conduits written by Joshua D. Mortensen and published by . This book was released on 2009 with total page 65 pages. Available in PDF, EPUB and Kindle. Book excerpt: While there has been a great deal of research on air entrainment at hydraulic jumps within closed conduits, very little of the research has specifically addressed size and temperature scale effects. Influences from jump location and changing length characteristics on air entrainment have also received little attention from past research. To determine the significance of size-scale effects of air entrained by hydraulic jumps in closed conduits, air flow measurements were taken in four different-sized circular pipe models with similar Froude numbers. Each of the pipe models sloped downward and created identical flow conditions that differed only in size. Additionally, specific measurements were taken in one of the pipe models with various water temperatures to identify any effects from changing fluid properties. To determine the significance of the effects of changed length characteristics on air demand, air flow measurements were taken with hydraulic jumps at multiple locations within a circular pipe with two different air release configurations at the end of the pipe. iii Results showed that air demand was not affected by the size of the model. All together, the data from four different pipe models show that size-scale effects of air entrained into hydraulic jumps within closed conduits are negligible. However, it was determined that air entrainment was significantly affected by the water temperature. Water at higher temperatures entrained much less air than water at lower temperatures. Hydraulic jump location results showed that for both configurations the percentage of air entrainment significantly increased as the hydraulic jump occurred near the point of air release downstream. As the jump occurred nearer to the end of the pipe, its length characteristics were shortened and air demand increased. However, jump location was only a significant factor until the jump occurred some distance upstream where the length characteristics were not affected. Upstream of this location the air demand was dependent only on the Froude number immediately upstream of the jump.

Download or read book Air Problems in Pipelines written by Manuela Escarameia and published by . This book was released on 2005-01-01 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Air Bubble Entrainment in Free Surface Turbulent Shear Flows written by Hubert Chanson and published by Elsevier. This book was released on 1996-10-11 with total page 403 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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

Download or read book Air Entrainment in Flowing Water written by Owen P. Lamb and published by . This book was released on 1949 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Air Entrainment in Free surface Flow written by I.R. Wood and published by Routledge. This book was released on 2018-04-24 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Selected Water Resources Abstracts written by and published by . This book was released on 1982 with total page 1060 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Computational Study on Hydraulic Jumps Including Air Entrainment written by Di Ning and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Scientific and engineering interest in hydraulic jumps has been sustained over the past several decades due to the importance of hydraulic jumps in natural and engineered open-channel flows. Over the last four decades, multiphase flow knowledge of hydraulic jumps has made considerable progress owing to experimental and theoretical studies, as well as computational models. However, most of the previous numerical simulations of hydraulic jumps ignored the two-phase nature of the flow and took the conventional one-phase approach.The first goal of this thesis is to build a comprehensive two-phase flow model of air-water mixture in hydraulic jumps, in order to investigate the internal flow features through computational methods. Building on the previous efforts and studies by Bombardelli and Garcia (1999), Gonzalez and Bombardelli (2005) and Waltz (2010), new two-phase flow models were developed in this study, using a state-of-the-art code, FLOW-3D®, to replicate the experimental works of Liu et al. (2004) and Murzyn et al. (2005).In order to obtain better solutions for hydraulic jumps and relative phenomena, the application of different numerical methods and different parameters used in numerical models are discussed in this thesis. With the help of the k-[varepsilon] two equation turbulence model and the Renormalization Group (RNG) k-[varepsilon] model, different parameters were chosen in order to find the best approach to simulate and estimate the flow velocities and air concentrations in hydraulic jumps. In our study, different patterns of the transportation of air (i.e. bubbles) in k-[varepsilon] model and RNG model were found, which were due to the different governing equations applied in these two numerical models to simulate the fate of air bubbles. Despite of the differences results, similar velocity and turbulent kinetic energy (TKE) distributions in most cross-sections were obtained, and they both have good agreement with the conclusions of previous studies by Chanson (2000), Gonzalez and Bombardelli (2005) and others. Furthermore, two- and three-dimensional (2D and 3D) simulations were also conducted in this study and similar numerical results were obtained based the comparison of TKE and velocity distribution in specific cross-sections in x-direction.

Download or read book A Study on Internal Flow Features and Air Entrainment Effects in Hydraulic Jumps Using Numerical Modeling Techniques written by Joseph Daniel Waltz and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In spite of the general impression that the hydraulic jump is a well-known flow phenomenon, detailed theoretical and numerical models of the internal flow features in hydraulic jumps have yet to be developed. The purpose of this thesis is to model internal flow features as well as air entrainment in hydraulic jump through numerical means, in two dimensions, using two-phase flow theory. In particular, this paper stems off the numerical works already started by Gonzalez and Bombardelli (2005) in which the authors replicated the experimental works of Liu. et. al. (2004) through a sluice gate and flume setup. Two-phase flow models were executed using a state-of-the-art code that incorporates air entrainment at the free surface. The commercial code FLOW-3D® uses computational fluid dynamics (CFD) in which standard flow equations are discretized and solved in each user-defined cell. The mathematical model equations are solved by the method of finite volumes/finite differences in Cartesian space. Different numerical models were run with different input conditions and setups. First, a replication of the works by Gonzalez and Bombardelli (2005) yielded very similar data in terms of horizontal velocity profiles and total kinetic energy profiles. Next, the location of the upstream boundary condition was moved farther upstream and no significant effect was observed. Three other implementations were performed to account for a dip in water elevation directly behind the sluice gate. The first was a raised sluice gate that yielded a jump toe elevation at the height of the original simulation setup. Next, a fixed uniform velocity boundary condition was implemented to assure only initial movement in the horizontal direction. Lastly, a streamlined lip as presented by Liu et. al. (2004) in their experimental works was applied to the setup. It was observed that hydraulic jump flow characteristics differed from experimental data when steering from the original sluice gate setup. This is likely due to an unclearness of the experimental setup, namely intrusive measuring devices and a lack of error measurements presented in the literature. These simulations were also only run for a relatively low Froude number of 2.

Download or read book Air Bubble Entrainment in Hydraulic Jumps written by Hubert Chanson and published by . This book was released on 2006-01-01 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Air Bubble Entrainment and Gas Transfer at Hydraulic Jumps written by H. Chanson and published by . This book was released on 1994 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Geomorphic Structure and Function of Hydraulic Jumps in Mountain River Channels written by Brett Landis Vallé and published by . This book was released on 2005 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Free Surface Hydraulics written by Dr J M Townson and published by CRC Press. This book was released on 1990-11-22 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: Free-Surface Hydraulics is a unified, pragmatic account of the water surface and its underlying mechanics. Based on the author's 30 years experience of research and teaching in civil engineering hydraulics, this text is designed to help students achieve a coherent understanding More...of a subject often obscured by empirical detail and unstructured approaches. The text leads progressively from hydrostatics, through steady and unsteady flows, to waves and tides. The author draws a careful distinction between kinematic and dynamic motions - the latter he treats at some length by the method of characteristics, regarded as one of the more rigorous approaches to unsteady flow. A special feature is the final chapter, devoted to the disruption of free surfaces by air and bubble motion, especially in pipes.

Download or read book Numerical Study of Two phase Turbulent Flow in Hydraulic Jumps written by Seyedpouyan Ahmadpanah and published by . This book was released on 2017 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hydraulic jump is a rapidly varied flow phenomenon that the flow changes suddenly from supercritical to subcritical. Hydraulic jumps are frequently observed to exist in natural river channels, streams, coastal water, and man-made water conveyance systems. Because of a sudden transition of flow regime, hydraulic jumps result in complex flow structures, strong turbulence, and air entrainment. Accordingly, they are two-phase flow, with air being the gas phase and water being the liquid phase. Consequences of the occurrence of hydraulic jumps include: unwanted fluctuations in the water surface with unstable waves and rollers, undesirable erosion of channel sidewalls and channel bottom, and reduced efficiency for water conveyance systems. Thus, it is important to study various aspects of the phenomenon.So far, knowledge of the phenomenon is incomplete. The main objective of this research is to improve our understanding of the complex flow structures and distributions of air entrainment in a hydraulic jump. Previously, both experimental and computational studies of the phenomenon have typically suffered a scale problem. The dimensions of the setup being used were unrealistically too small.In this research, we took the computational fluid dynamics (CFD) approach, and simulated hydraulic jumps at relatively large and practical dimensions. This would help reduce artificial scale effects on the results. On the basis of Reynolds averaged continuity and momentum equations, CFD simulations of hydraulic jumps were performed for four different cases in terms of the approach flow Froude number Fr1, ranging from 3.1 to 5.1. The Reynolds number is high (between 577662 and 950347), which ensures turbulent flow conditions. The CFD model channel is discretized into 2,131,200 cells. The mesh has nearly uniform structures, with fine spatial resolutions of 2.5 mm. The volume of fluid method provides tracking of the free surface. The standard k-f turbulence model provides turbulence closure.For each of the simulation cases, we carried out analyses of time-averaged air volume fraction, time-averaged velocity, time- and depth-averaged (or double averaged) air volume fraction at a series of locations along the length of the model channel (Note that the terms air volume fraction and void fraction are used interchangeably in this thesis). We compared the CFD predictions of air volume fraction with available laboratory measurements. It is important to note that these measurements were made from laboratory experiments that corresponded to essentially the same values of Fr as this CFD study, but used a channel of smaller dimensions, in comparison to the CFD model channel. The CFD results of time-averaged air volume fraction are reasonable, when compared to the experimental data, except for the simulation case with Fr1 = 3.8. For all the four simulation cases, the predicted variations in air volume fraction show a trend in consistency with the experimental results. For the three simulation cases (with Fr1 = 3.1, 3.8 and 4.4), the time-averaged air volume fraction in the hydraulic jumps is larger at higher Reynolds number. However, for the simulation case with Fr1 = 5.1, it is smaller at higher Reynolds number. This implies that the amount of air being entrained into a hydraulic jump depends on not only Fr1 but also the depth of the approach flow. In future studies of the hydraulic jump phenomenon, one should consider using approach flow of realistically large dimensions at various values of Fr1, for realistic predictions of air entrainment in hydraulic jump rollers.

Download or read book Symposium on Scale Effects in Modelling Hydraulic Structures written by Helmut Kobus and published by Institut Fur Wasserbau Universitat Stuttgart. This book was released on 1985 with total page 608 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Behaviour of the Hydraulic Jump in a Closed Conduit written by J. R. Scott and published by . This book was released on 1965 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Air release Air vacuum and Combination Air Valves written by and published by American Water Works Association. This book was released on 2001 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt: Operators, technicians, and engineers will find the information in this manual useful for gaining a basic understanding of the use and application of air valves. A valuable guide for selecting, sizing, locating, and installing air valves in water applications, M51 provides information on air valve types listed in AWWA Standard C512, latest edition, including the following: air-release valve; air/vacuum valve; and combination air valve.

Download or read book Comptes Rendus written by International Association for Hydraulic Research. Congress and published by . This book was released on 1977 with total page 1176 pages. Available in PDF, EPUB and Kindle. Book excerpt: