Download or read book A Simple and Efficient Diffuse Interface Method for Compressible Two Phase Flows written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In nuclear reactor safety and optimization there are key issues that rely on in-depth understanding of basic two-phase flow phenomena with heat and mass transfer. For many reasons, to be discussed, there is growing interest in the application of two-phase flow models to provide diffuse, but nevertheless resolved, simulation of interfaces between two immiscible compressible fluids - diffuse interface method (DIM). Because of its ability to dynamically create interfaces and to solve interfaces separating pure media and mixtures for DNS-like (Direct Numerical Simulation) simulations of interfacial flows, we examine the construction of a simple, robust, fast, and accurate numerical formulation for the 5-equation Kapila et al. [1] reduced two-phase model. Though apparently simple, the Kapila et al. model contains a volume fraction differential transport equation containing a nonlinear, non-conservative term which poses serious computational challenges. To circumvent the difficulties encountered with the single velocity and single pressure Kapila et al. [1] multiphase flow model, a 6-equation relaxation hyperbolic model is built to solve interface problems with compressible fluids. In this approach, pressure non-equilibrium is first restored, followed by a relaxation to an asymptotic solution which is convergent to the solutions of the Kapila et al. reduced model. The apparent complexity introduced with this extended hyperbolic model actually leads to considerable simplifications regarding numerical resolution, and the various ingredients used by this method are general enough to consider future extensions to problems involving complex physics.
Download or read book A Novel Diffuse interface Model and Numerical Methods for Compressible Turbulent Two phase Flows and Scalar Transport written by Suhas Jain Suresh and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Compressible two-phase flows and the transport of scalars in two-phase flows have a wide range of applications in natural and engineering processes. In this thesis we first present a novel diffuse-interface model for the simulation of compressible two-phase flows. We start with the baseline five-equation model that consists of equations for the transport of volume fraction, mass of each phase, momentum, and total energy. It is known that this model cannot be used with a non-dissipative scheme as is, and the direct solution of these equations with a dissipative scheme results in artificial diffusion of the interface which results in poor accuracy. We, therefore, propose interface-regularization (diffusion--sharpening) terms to this five-equation model in such a way that the resulting model can now be used with a non-dissipative central scheme, and the model also maintains the discrete conservation of mass of each phase, momentum, and total energy of the system. For stable numerical simulations of compressible flows, it is known that a discrete entropy condition needs to be satisfied, and the discrete conservation of kinetic energy alone is not a sufficient condition, unlike in incompressible flows. To achieve this, we first propose discrete consistency conditions between the numerical fluxes, and then present a set of numerical fluxes--which satisfies these consistency conditions--that results in an exact discrete conservation of kinetic energy and approximate conservation of entropy (a KEEP scheme) in the absence of pressure work, viscosity, and thermal diffusion effects. Next, we also propose a novel scalar-transport model for the simulation of scalar quantities in two-phase flows. In a two-phase flow, the scalar quantities typically have very different diffusivities in the two phases, which results in effective confinement of the scalar quantities in one of the phases, in the time scales of interest. This confinement of the scalars leads to the formation of sharp gradients of the scalar concentration values at the interface and could result in artificial numerical leakage of the scalar and negative values for the scalar concentration values, presenting a serious challenge for its numerical simulations. To overcome this challenge, we propose a new consistent scalar-transport model that prevents artificial numerical leakage of the scalar at the interface. The proposed model also maintains the positivity property of the scalar concentration field, a physical realizability requirement for the simulation of scalars. Finally, we present numerical simulations to verify and validate the models presented in this work in a wide range of settings and regimes, spanning laminar to turbulent flows; and assess the accuracy, robustness, and scalability of the models.
Download or read book Multiphase Microfluidics The Diffuse Interface Model written by Roberto Mauri and published by Springer Science & Business Media. This book was released on 2012-05-31 with total page 181 pages. Available in PDF, EPUB and Kindle. Book excerpt: Diffuse interface (D.I.) model for muliphase flows.- Phase separation of viscous ternary liquid mixtures.- Dewetting and decomposing films of simple and complex liquids.- Phase-field models. Multiphase flows are typically described assuming that the different phases are separated by a sharp interface, with appropriate boundary conditions. This approach breaks down whenever the lengthscale of the phenomenon that is being studied is comparable with the real interface thickness, as it happens, for example, in the coalescence and breakup of bubbles and drops, the wetting and dewetting of solid surfaces and, in general, im micro-devices. The diffuse interface model resolves these problems by assuming that all quantities can vary continuously, so that interfaces have a non-zero thickness, i.e. they are "diffuse". The contributions in this book review the theory and describe some relevant applications of the diffuse interface model for one-component, two-phase fluids and for liquid binary mixtures, to model multiphase flows in confined geometries.
Download or read book A Robust and Efficient Finite Volume Method for Compressible Two Phase Flows at All Speeds on Unstructured Grids written by Aditya Kiran Pandare and published by . This book was released on 2018 with total page 131 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Proceedings of the 4th International Seminar on Non Ideal Compressible Fluid Dynamics for Propulsion and Power written by Martin White and published by Springer Nature. This book was released on 2023-05-01 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book collects the main contributions from the 4th edition of the NICFD conference, organized by the Special Interest Group on Non-Ideal Compressible Fluid Dynamics (SIG- 49). It provides some of the latest research findings in the field of NICFD, relevant to a number of engineering applications related to the conversion of renewable and waste energy sources, like, e.g., organic Rankine cycles, super-critical CO2 cycle power plants, combustors operating with supercritical fluids, and heat pumps. The book reports on research encompassing theoretical, computational, and experimental aspects of the gas-dynamics of non-ideal reactive and non-reactive flows and their impact for the design of internal-flow components (turbomachinery, heat exchangers, combustors). All chapters address challenges related to characterizing the behaviour of non-ideal fluids, where state-of-the-art models are used to predict the thermo-physical properties of both pure and multi-phase fluids.
Download or read book A Novel Diffuse Interface Method for Two phase Flows and Application in Simulation of Micro bubble Entrainment written by Seyedshahabaddin Mirjalili and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Micro-bubbles have been observed in various contexts such as in raindrops impacting liquid pools, boiling heat transfer, aerosol generation, breaking oceanic waves and ship wakes. Due to their long residence time under the free surface, micro-bubbles impact air-sea mass transport, formation of white caps and the signature of seafaring vessels. As such, understanding the mechanism involved in the formation of these bubbles is of significant interest. Based on evidence from drop-pool impact experiments, the leading hypothesis for micro-bubble formation is that when liquid interfaces collide, a thin gas film is entrapped, which leaves behind hundreds of micro-bubbles as it retracts. Due to the wide range of length and time scales involved, there is a lack of understanding of this mechanism, in addition to quantitative data regarding the generated micro-bubbles. This physical understanding has significant practical value, as one seeks to model micro-bubbles in large scale turbulent two-phase flow simulations. In the first portion of this thesis, we present a novel diffuse interface method for simulation of incompressible, immiscible two-phase flows. The boundedness of this mass-conserving interface-capturing method is proven, and a comparison of the fully coupled solver with a state-of-the-art two-phase flow solver is provided. Then, we show how the momentum transport equation must be modified to achieve consistency with mass transport and conservation of momentum and kinetic energy. The practical importance of this correction, and our method's capability in modeling turbulent two-phase flows, is demonstrated via simulations of a liquid jet in cross-flow. Finally, we present a robust method for representation of surface tension forces that utilizes discrete surface energy definition. Overall, the desirable conservation properties, robustness, mass-momentum consistency, simplicity and parallel scalability render our method a promising and viable option for realistic two-phase flow simulations. In the second portion of the thesis, we study the impact of a drop on a deep liquid pool as an appropriate model problem for understanding how collisions between two arbitrarily-curved interfaces may lead to micro-bubble entrainment. Using numerical simulations with a boundary integral method, we explain the physics of thin gas film entrapment and the stages of its evolution. These numerical simulations, in addition to theoretical arguments, lead to the discovery of a transition in the dynamics of the thin gas film that is necessary for entrapment of high aspect ratio films that can shed micro-bubbles. After presenting our study on thin gas film entrapment, we employ our diffuse interface method to numerically simulate thin retracting gas films. A new scaling law for gas film retraction velocity is found. Moreover, using high-fidelity 3D simulations, we find that a transverse instability on the edge of the film is responsible for micro-bubble generation. By combining our findings from the drop-pool impact simulations and the thin gas film retraction simulations, we provide the means for subgrid-scale modeling of micro-bubbles in large scale two-phase flows.
Download or read book Analysis of Diffuse Interface Models for Two phase Flows with and Without Surfactants written by Josef Thomas Weber and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Two Phase Flows written by Shih-i Pai and published by Springer-Verlag. This book was released on 2013-07-02 with total page 373 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 Numerical Modeling of Compressible Two phase Flows with a Pressure based Method written by Markus Boger and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Flowing Matter written by Federico Toschi and published by Springer Nature. This book was released on 2019-09-25 with total page 309 pages. Available in PDF, EPUB and Kindle. Book excerpt: This open access book, published in the Soft and Biological Matter series, presents an introduction to selected research topics in the broad field of flowing matter, including the dynamics of fluids with a complex internal structure -from nematic fluids to soft glasses- as well as active matter and turbulent phenomena. Flowing matter is a subject at the crossroads between physics, mathematics, chemistry, engineering, biology and earth sciences, and relies on a multidisciplinary approach to describe the emergence of the macroscopic behaviours in a system from the coordinated dynamics of its microscopic constituents. Depending on the microscopic interactions, an assembly of molecules or of mesoscopic particles can flow like a simple Newtonian fluid, deform elastically like a solid or behave in a complex manner. When the internal constituents are active, as for biological entities, one generally observes complex large-scale collective motions. Phenomenology is further complicated by the invariable tendency of fluids to display chaos at the large scales or when stirred strongly enough. This volume presents several research topics that address these phenomena encompassing the traditional micro-, meso-, and macro-scales descriptions, and contributes to our understanding of the fundamentals of flowing matter. This book is the legacy of the COST Action MP1305 “Flowing Matter”.
Download or read book Fundamentals of Engineering Numerical Analysis written by Parviz Moin and published by Cambridge University Press. This book was released on 2010-08-23 with total page 257 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the original publication of this book, available computer power has increased greatly. Today, scientific computing is playing an ever more prominent role as a tool in scientific discovery and engineering analysis. In this second edition, the key addition is an introduction to the finite element method. This is a widely used technique for solving partial differential equations (PDEs) in complex domains. This text introduces numerical methods and shows how to develop, analyse, and use them. Complete MATLAB programs for all the worked examples are now available at www.cambridge.org/Moin, and more than 30 exercises have been added. This thorough and practical book is intended as a first course in numerical analysis, primarily for new graduate students in engineering and physical science. Along with mastering the fundamentals of numerical methods, students will learn to write their own computer programs using standard numerical methods.
Download or read book Computational Methods for Multiphase Flow written by Andrea Prosperetti and published by Cambridge University Press. This book was released on 2009-06-25 with total page 392 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thanks to high-speed computers and advanced algorithms, the important field of modelling multiphase flows is an area of rapid growth. This one-stop account – now in paperback, with corrections from the first printing – is the ideal way to get to grips with this topic, which has significant applications in industry and nature. Each chapter is written by an acknowledged expert and includes extensive references to current research. All of the chapters are essentially independent and so the book can be used for a range of advanced courses and the self-study of specific topics. No other book covers so many topics related to multiphase flow, and it will therefore be warmly welcomed by researchers and graduate students of the subject across engineering, physics, and applied mathematics.
Download or read book Elements of Continuum Mechanics and Conservation Laws written by S.K. Godunov and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 263 pages. Available in PDF, EPUB and Kindle. Book excerpt: Elements of Continuum Mechanics and Conservation Laws presents a systematization of different models in mathematical physics, a study of the structure of conservation laws, thermodynamical identities, and connection with criteria for well-posedness of the corresponding mathematical problems. The theory presented in this book stems from research carried out by the authors concerning the formulations of differential equations describing explosive deformations of metals. In such processes, elasticity equations are used in some zones, whereas hydrodynamics equations are stated in other zones. Plastic deformations appear in transition zones, which leads to residual stresses. The suggested model contains some relaxation terms which simulate these plastic deformations. Certain laws of thermodynamics are used in order to describe and study differential equations simulating the physical processes. This leads to the special formulation of differential equations using generalized thermodynamical potentials.
Download or read book Immersed Boundary Method written by Somnath Roy and published by Springer Nature. This book was released on 2020-05-15 with total page 441 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume presents the emerging applications of immersed boundary (IB) methods in computational mechanics and complex CFD calculations. It discusses formulations of different IB implementations and also demonstrates applications of these methods in a wide range of problems. It will be of special value to researchers and engineers as well as graduate students working on immersed boundary methods, specifically on recent developments and applications. The book can also be used as a supplementary textbook in advanced courses in computational fluid dynamics.
Download or read book Diffuse Interface Models for Two phase Flows of Viscous Incompressible Fluids written by Helmut Abels and published by . This book was released on 2008 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Computational Methods for Compressible Two phase Flows written by Erik Burman and published by . This book was released on 1996 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt:
