Download or read book Numerical Simulation and Analysis of Shock Phenomena in Cavitating Flow and Its Application to Ship Propellers written by Bernd Budich and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Cavitation Instabilities and Rotordynamic Effects in Turbopumps and Hydroturbines written by Luca d'Agostino and published by Springer. This book was released on 2017-03-17 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book provides a detailed approach to the physics, fluid dynamics, modeling, experimentation and numerical simulation of cavitation phenomena, with special emphasis on cavitation-induced instabilities and their implications on the design and operation of high performance turbopumps and hydraulic turbines. The first part covers the fundamentals (nucleation, dynamics, thermodynamic effects, erosion) and forms of cavitation (attached cavitation, cloud cavitation, supercavitation, vortex cavitation) relevant to hydraulic turbomachinery, illustrates modern experimental techniques for the characterization, visualization and analysis of cavitating flows, and introduces the main aspects of the hydrodynamic design and performance of axial inducers, centrifugal turbopumps and hydo-turbines. The second part focuses on the theoretical modeling, experimental analysis, and practical control of cavitation-induced fluid-dynamic and rotordynamic instabilities of hydraulic turbomachinery, with special emphasis on cavitating turbopumps (cavitation surge, rotating cavitation, higher order cavitation surge, rotordynamic whirl forces). Finally, the third part of the book illustrates the alternative approaches for the simulation of cavitating flows, with emphasis on both modeling and numerical aspects. Examples of applications to the simulation of unsteady cavitation in internal flows through hydraulic machinery are illustrated in detail.
Download or read book A Numerical Study of Cavitating Flows Based on Plic vof Method for Arbitrary Unstructured Meshes written by Dezhi Dai and published by . This book was released on 2022 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cavitation appears when local static pressure drops below the water vapor pressure and causes significant impacts on marine propeller blades. The Volume of Fluid (VOF) method, which is also referred to as the Transport Equation-based Model (TEM), has been extensively adopted in the cavitating flow simulations. Piecewise Linear Interface Calculation (PLIC) schemes have been extensively employed in the VOF method for interface capturing in numerical simulations of multiphase flows. Polyhedral unstructured meshes are often adopted due to their geometric flexibility and superiority in gradient calculation. Four analytical interface reconstruction algorithms in the PLIC-VOF method for arbitrary convex polyhedral cells have been proposed in the present study. The plane interface at a given orientation within a polyhedral cell is located by four different analytical techniques. They have been tested successfully for six different geometric shapes that are common in polyhedral meshes. The computational efficiencies of the algorithms have been compared with two other published schemes in the literature. The proposed algorithms have been shown to yield smaller truncation errors with a reduction in computational complexity. A numerical simulation of a 3D dam-breaking problem has been successfully performed using the proposed interface reconstruction scheme on a polyhedral mesh. The percentage of the overall computational time consumed has been assessed to justify its optimization in a real multiphase flow simulation. The effects of cavitation on the dynamics of a two-dimensional hydrofoil and three-dimensional propeller have been studied numerically. Analytical PLIC-VOF methods on overset unstructured meshes have been employed to capture the interface between liquid and vapor phases in cavitating flows around a NACA 66 (MOD) hydrofoil and PPTC propeller. A modified version of the Schnerr-Sauer cavitation model has been adopted to compute the local mass transport rate for the vaporization and condensation processes. Turbulent eddy viscosity is evaluated by using the Spalart-Allmaras one-equation model. Simulations are performed under the framework of OpenFOAM with a modified flow solver. Stable sheet and unstable cloud cavitations have been investigated. The findings in the present study are consistent with experimental studies reported in the literature.
Download or read book Numerical Simulation of Cavitating and Non cavitating Flows Over a Hydrofoil written by and published by . This book was released on 1997 with total page 83 pages. Available in PDF, EPUB and Kindle. Book excerpt: The compressible hydrodynamic approach previously developed for small Mach number non-cavitating flows has been extended to simulate cavitating flows as well as non-cavitating flows. The extension is made possible by assuming a complex equation of state relating density and pressure to cover the liquid phase and the gas phase. Thus, the cavitation phenomenon is regarded as a single-phase flow phenomenon enabling the elimination of the cavity closure condition. The numerical model is an unsteady 3-dimensional flow model based on a large eddy simulation approach. It is applied to typical thin hydrofoils and thick hydrofoils at non-cavitating conditions and various cavitating flow conditions, including moving cavity, stable sheet cavity and sheet cavity/cloud cavity cyclical flow conditions. Computations are carried out primarily for 2-dimensional foils, but 3-dimensional flow characteristics are also examined. The computational results are compared with some available data; good quantitative and qualitative agreements are indicated. It is considered very significant that the sheet cavitation/cloud cavitation phenomenon is found to be similar to the viscous boundary layer flow separation/vortex shedding and washout phenomenon in many respects. Cavitation is found to trigger boundary layer separation in otherwise non-separated flow.
Download or read book Applied mechanics reviews written by and published by . This book was released on 1948 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Cavitation and Bubble Dynamics written by Foivos Koukouvinis and published by Elsevier. This book was released on 2021-09-24 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cavitation and Bubble Dynamics: Fundamentals and Applications examines the latest advances in the field of cavitation and multiphase flows, including associated effects such as material erosion and spray instabilities. This book tackles the challenges of cavitation hindrance in the industrial world, while also drawing on interdisciplinary research to inform academic audiences on the latest advances in the fundamentals. Contributions to the book come from a wide range of specialists in areas including fuel systems, hydropower, marine engineering, multiphase flows and computational fluid mechanics, allowing readers to discover novel interdisciplinary experimentation techniques and research results. This book will be an essential tool for industry professionals and researchers working on applications where cavitation hindrance affects reliability, noise, and vibrations. Covers a wide range of cavitation and bubble dynamics phenomena, including shock wave emission, jetting, and luminescence Provides the latest advice about applications including cavitation tunnels, cavitation testing, flow designs to avoid cavitation in pumps and other hydromachinery, and flow lines Describes novel experimental techniques, such as x-ray imaging and new computational techniques
Download or read book Numerical Simulation of Cavitating Bubble laden Turbulent Flows written by Ehsan Shams Sobhani and published by . This book was released on 2010 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many engineering devices and propulsion systems suffer from undesirable effects of cavitation; such as degradation in the efficiency of pumps and turbines, generation of noise and vibration on ship propeller, increased drag and erosion of propeller blade, etc. In spite of decades of research on this problem, detailed study of cavitation physics is still a technical challenge for the current experimental and numerical approaches. Further development of robust and accurate numerical methods for cavitating flow simulation, is the basis of this research. The main objective of this research is to investigate traveling bubble cavitation in turbulent flows. Variable density Navier-Stokes equations are solved in an unstructured grid finite volume solver. Large Eddy Simulation technique with dynamic Smagorinsky subgrid model is used for turbulence modeling. Bubble cavitation is modeled in a Lagrangian framework with subgrid models for forces acting on bubbles. Bubble size variation is modeled using local flow field hydrodynamic pressure for solving Rayliegh-Plesset equation. An adaptive time stepping method is devised for the efficient solution of this highly non-linear equation. Turbulent flow over an open cavity is reproduced numerically from the experimental work by [Liu and Katz, PoF, 08]. Flow statistics agreed very well to those of experiment. Cavitation inception was studied using two different models: (i) discrete bubble model, and (ii) scalar transport model. Severe cavitation was predicted near on top of the trailing edge for cavitation index of [delta]
Download or read book Cavitating Flow Over Stationary and Oscillating Hydrofoils written by and published by . This book was released on 2008 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: Modern ships are usually designed for a broad range of sea conditions. In particular, much of the effort during ship design is focused on reduction of ship roll due to rough sea. Ship roll has always been of significant concern as it largely affects the ship performance. In order to mitigate the detrimental effects of ship roll, many kinds of ship stabilization systems have been tried and tested. One such system that is currently investigated in this work is the active-fin ship stabilization system. It consists of a system of dynamically oscillating hydrofoils, responding to cancel ship roll by producing counter acting lift. Below the dynamic stall angle, the lift force produced by hydrofoils is proportional to angle of attack. So ship stabilization systems are often operated between large angles of attack. However, at large angle of attack, a region of low pressure forms over the suction side of the hydrofoil. The low pressure results in localized increase in cavitation. Cavitation affects the performance of fin stabilization systems, and it is therefore necessary to study and understand the flow physics involving cavitation, occurring over on oscillating fin stabilizers. In this study, the active fin stabilization system is simplified to a 2D NACA0015 hydrofoil geometry, and the aperiodic fin oscillation is simplified to a periodic hydrofoil oscillation and, to stay close to reality, a near trapezoidal hydrofoil oscillation profile is used. The present work is a contribution to the numerical simulation of cavitating flows over 2D NACA 0015 stationary and oscillating hydrofoils. The primary objective of this research is to establish a methodology to accurately identify the onset of cavitation, and to study and quantify the deleterious effects of cavitation on performance. In order to investigate and quantify the detrimental effects of cavitation on the present ship stabilization system, the commercial flow solver FLUENT v6.3 is employed. A detailed formulation of the numerical model is described, and its application to simulate cavitating flow over stationary and oscillating 2D NACA 0015 hydrofoils is demonstrated. Validation studies for the turbulence viscosity modifications for the RNG k epsilon equation have been presented. For both the stationary and oscillating cases, good agreement between the predictions and measurements is obtained. Simulation of cavitating flow over stationary hydrofoils is carried out, to understand the different steady and unsteady cavitating regimes, and to identify an approximate cavitation inception angle. The scillating hydrofoil analysis is carried out using a dynamic hybrid grid where the boundaries of the outer domain are fixed, and the hydrofoil and the inner domain surrounding the hydrofoil oscillate periodically according to a prescribed profile non sinusoidal. A user defined function (UDF) is coupled with the flow solver to oscillate the hydrofoil with its prescribed oscillation profile. A comparative study on effects of grid topology, flow regime and cavitation has been carried out at 5 Reynolds numbers.
Download or read book Fundamentals of Cavitation written by Jean-Pierre Franc and published by Springer Science & Business Media. This book was released on 2006-01-22 with total page 321 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book treats cavitation, which is a unique phenomenon in the field of hyd- dynamics, although it can occur in any hydraulic machinery such as pumps, propellers, artificial hearts, and so forth. Cavitation is generated not only in water, but also in any kind of fluid, such as liquid hydrogen. The generation of cavitation can cause severe damage in hydraulic machinery. Therefore, the prevention of cavitation is an important concern for designers of hydraulic machinery. On the contrary, there is great potential to utilize cavitation in various important applications, such as environmental protection. There have been several books published on cavitation, including one by the same authors. This book differs from those previous ones, in that it is both more physical and more theoretical. Any theoretical explanation of the cavitation phenomenon is rather difficult, but the authors have succeeded in explaining it very well, and a reader can follow the equations easily. It is an advantage in reading this book to have some understanding of the physics of cavitation. Therefore, this book is not an introductory text, but a book for more advanced study. However, this does not mean that this book is too difficult for a beginner, because it explains the cavitation phenomenon using many figures. Therefore, even a beginner on cavitation can read and can understand what cavitation is. If the student studies through this book (with patience), he or she can become an expert on the physics of cavitation.
Download or read book Cavitation and Bubble Dynamics written by Christopher E. Brennen and published by Cambridge University Press. This book was released on 2014 with total page 269 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cavitation and Bubble Dynamics deals with fundamental physical processes of bubble dynamics and cavitation for graduate students and researchers.
Download or read book The Hydrodynamics of Cavitating Flows written by Alexey G.. Terentiev and published by . This book was released on 2011 with total page 598 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experimental Study of the Structure and Dynamics of Cavitating Flows written by Guangjian Zhang and published by Scientific Research Publishing, Inc. USA. This book was released on 2023-11-06 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cavitation refers to a distinctive occurrence within liquid flows where there is a phase change process involving the rapid transformation of liquid into vapour in regions of low pressure, followed by collapsing or implosion when pressure rises again. The study of cavitation dates back to the late 19th century. While the term “cavitation” was originally coined by R. E. Froude and first documented by Barnaby and Thornycroft in 1895, the concept had been speculated upon much earlier by L. Euler in his 1754 theory on water turbines. However, the phenomenon of cavitation was initially observed and examined by Barnaby and Parsons in 1893. They identified that the formation of vapour bubbles on propeller blades had led to the failure of the sea trial of the British high-speed warship HMS Daring in 1885. In 1895, Parsons established the first water tunnel dedicated to cavitation research, revealing the connection between cavitation and propeller damage. The theoretical groundwork for cavitation research was laid by Rayleigh in 1917, as he successfully addressed the collapse of an empty cavity within a substantial liquid mass. Since then, numerous research work has been published on cavitating flow.
Download or read book Supercavitation written by Igor Nesteruk and published by Springer Science & Business Media. This book was released on 2012-01-11 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt: This collection is dedicated to the 70th jubilee of Yu. N. Savchenko, and presents experimental, theoretical, and numerical investigations written by an international group of well-known authors. The contributions solve very important problems of the high-speed hydrodynamics,such as supersonic motion in water, drag diminishing, dynamics and stability of supercavitating vehicles, water entry and hydrodynamic performances of hydrofoils, ventilated cavities after a disc and under the ship bottom. The book is written for researches, scientists, engineers, and students interested in problems of hydromechanics.
Download or read book Predicting Cavitation induced Noise from Marine Propellers written by Duncan McIntyre and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Noise pollution threatens marine ecosystems, where animals rely heavily on sound for navigation and communication. The largest source of underwater noise from human activity is shipping, and propeller-induced cavitation is the dominant source of noise from ships. Mitigation strategies require accurate methods for predicting cavitation-induced noise, which remains challenging. The present thesis explores prediction and modelling strategies for cavitation-induced noise from marine propellers, and provides insight into models that can be used both during propeller design and to generate intelligent vessel control strategies. I examined three distinct approaches to predicting cavitation-induced noise, each of which is discussed in one of the three main chapters of this thesis: a high-fidelity computational fluid dynamics scheme, a parametric mapping procedure, and the use of field measurements. Each of these three chapters presents different insight into the acoustic behaviour of cavitating marine propellers, as well both real and potential strategies for mitigating this critical environmental emission. A combined experimental and numerical study of noise from a cavitating propeller, focused on both the fundamental importance of experimental findings and the effectiveness of the numerical modelling strategy used, is detailed in the first main chapter of this thesis. The experimental results highlighted that loud cavitation noise is not necessarily associated with high-power or high-speed propeller operation, affirming the need for intelligent vessel operation strategies to mitigate underwater noise pollution. Comparison of the experimental measurements and simulations revealed that the simulation strategy resulted in an over-prediction of sound levels from cavitation. Analysis of the numerical results and experiments strongly suggested that the cavitation model implemented in the simulations, a model commonly used for marine propeller simulations, was responsible for the over-prediction of sound levels. Ships are powered primarily by combustion engines, for which it is possible to generate "maps" relating the emission of pollutants to the engine's speed and torque; the second main chapter of this thesis presents the methodology I developed for generating similar "maps" relating the level of cavitation-induced noise to the speed and torque of a ship's propeller. A proof-of-concept of the method that used the model propeller from the first main chapter is presented. To generate the maps, I used a low-order simulation technique to predict the cavitation induced by the propeller at a range of different speed and torque combinations. A pair of semi-empirical models found in the literature were combined to provide the framework for predicting noise based on cavitation patterns. The proof-of-concept map shows a clear optimal operating regime for the propeller. The final main chapter of this thesis presents an analysis of field noise measurements of coastal ferries in commercial operation, the data for which were provided by an industrial partner. The key finding was the identification of cavitation regime changes with variation in vessel speed by their acoustic signatures. The results provide a basis for remotely determining which vessels produce less noise pollution when subject to speed limits, which have been implement in critical marine habitats, and which vessels produce less noise at a specific optimum speed.
Download or read book Numerical simulation and investigation of high speed bubble dynamics in cavitating flow written by Eric Lauer and published by . This book was released on 2013 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Cavitation and Bubble Dynamics written by Christopher Earls Brennen and published by Cambridge University Press. This book was released on 2013-10-14 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Cavitation and Bubble Dynamics deals with the fundamental physical processes of bubble dynamics and the phenomenon of cavitation. It is ideal for graduate students and research engineers and scientists, and a basic knowledge of fluid flow and heat transfer is assumed. The analytical methods presented are developed from basic principles. The book begins with a chapter on nucleation and describes both the theory and observations in flowing and non-flowing systems. Three chapters provide a systematic treatment of the dynamics and growth, collapse, or oscillation of individual bubbles in otherwise quiescent fluids. The following chapters summarise the motion of bubbles in liquids, describe some of the phenomena that occur in homogeneous bubbly flows, with emphasis on cloud cavitation, and summarise some of the experimental observations of cavitating flows. The last chapter provides a review of free streamline methods used to treat separated cavity flows with large attached cavities.
Download or read book Numerical Simulation and Analysis of Multi Scale Cavitating Flows Using a Hybrid Mixture Bubble Model written by Ebrahim Ghahramani and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
