Download or read book The Development of Efficient Techniques for Simulating Non continuum Gas Flows written by Craig Euler and published by . This book was released on 2013 with total page 77 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis is concerned with the development of efficient techniques for simulating non-continuum flows using model kinetic equations. High order nodal discontinuous Galerkin (DG) discretization in velocity space of the Bhatnagar-Gross-Krook (BGK) and Ellipsoidal-Statistical Bhatnagar-Gross-Krook (ES-BGK) model kinetic equations are developed and implemented. The spatial and temporal discretization are implemented on the basis of the CLAWPACK software which is extended to solve the kinetic model equations. The author performs numerical simulations of the heat transfer and the normal shock wave problems. Accuracy of the numerical solutions in satisfying the conservation laws is assessed. The author confirms that the solutions exhibit the expected order of convergence. In the problem of the normal shock wave the obtained numerical solutions are compared to experimental data. In the second part of the thesis, the problem of spatially homogeneous relaxation is considered. For this problem, a new conservative BGK model with velocity dependent collision frequency is designed. With the new model, one achieves the correct relaxation rates for a selected group of moments. The correct rates are obtained by solving the Boltzmann equation deterministically at the initial time step.
Download or read book Efficient Numerical Techniques for Multiscale Modeling of Thermally Driven Gas Flows with Application to Thermal Sensing Atomic Force Microscopy written by Nathan Daniel Masters and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The modeling of Micro- and NanoElectroMechanical Systems (MEMS and NEMS) requires new computational techniques that can deal efficiently with geometric complexity and scale dependent effects that may arise. Reduced feature sizes increase the coupling of physical phenomena and noncontinuum behavior, often requiring models based on molecular descriptions and/or first principles. Furthermore, noncontinuum effects are often localized to small regions of (relatively) large systemsprecluding the global application of microscale models due to computational expense. Multiscale modeling couples efficient continuum solvers with detailed microscale models to providing accurate and efficient models of complete systems. This thesis presents the development of multiscale modeling techniques for nonequilibrium microscale gas phase phenomena, especially thermally driven microflows. Much of this focuses on improving the ability of the Information Preserving DSMC (IP-DSMC) to model thermally driven flows. The IP-DSMC is a recent technique that seeks to accelerate the solution of direct simulation Monte Carlo (DSMC) simulations by preserving and transporting certain macroscopic quantities within each simulation molecules. The primary contribution of this work is the development of the Octant Splitting IP-DSMC (OSIP-DSMC) which recovers previously unavailable information from the preserved quantities and the microscopic velocities. The OSIP-DSMC can efficiently simulate flow fields induced by nonequilibrium systems, including phenomena such as thermal transpiration. The OSIP-DSMC provides an efficient method to explore rarefied gas transport phenomena which may lead to a greater understanding of these phenomena and new concepts for how these may be utilized in practical engineering systems. Multiscale modeling is demonstrated utilizing the OSIP-DSMC and a 2D BEM solver for the continuum (heat transfer) model coupled with a modified Alternating Schwarz coupling scheme. An interesting application for this modeling technique is Thermal Sensing Atomic Force Microscopy (TSAFM). TSAFM relies on gas phase heat transfer between heated cantilever probes and the scanned surface to determine the scan height, and thus the surface topography. Accurate models of the heat transfer phenomena are required to correctly interpret scan data. This thesis presents results demonstrating the effect of subcontinuum heat transfer on TSAFM operation and explores the mechanical effects of the Knudsen Force on the heated cantilevers.
Download or read book Rarefied Gas Flows in Microscale Geometries written by Stephanie Y. Docherty and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Accurate predictions of the flow behaviour in microscale geometries are needed, for example, to design and optimise micro devices, and to ensure their safety/reliability. Rarefied gas flows in such geometries tend, however, to be far from local thermodynamic equilibrium, meaning that the flow behaviour cannot be described by conventional fluid mechanics. Alternative approaches for modelling 'non-equilibrium' gas flows have been proposed in recent years; because analytical solution methods are subject to significant limitations, the direct simulation Monte Carlo (DSMC) method is, at present, the most practical numerical simulation tool for dilute gases. Unfortunately, the computational expense of tracking and computing collisions between thousands (or perhaps millions) of DSMC particles means that simulating the scales of realistic flow problems can require months (or even years) of computing time. This has resulted in the development of continuum-DSMC 'hybrid' methods, which aim to combine the efficiency of a conventional continuum-fluid description with the detail and accuracy of the DSMC method. This thesis focuses on the development of a continuum-DSMC method that offers a more general approach than existing methods. Using a heterogeneous framework with a field-wise coupling strategy, this new method is not subject to the limitations of the well-known domain decomposition framework, or the restrictions of the heterogeneous point-wise coupling approach. The continuum-fluid description is applied across the entire flow field, while the DSMC method is performed in dispersed micro elements that can be any size and at any location; these elements then provide the continuum description with updated constitutive and boundary information. Unlike most methods in the literature, the coupling strategy presented here is able to cope with heat transfer, and so non-isothermal flows can be simulated. Testing and validation of this new continuum-DSMC method is performed by simulating a number of benchmark cases and comparing the results with full DSMC solutions of the same cases. Two 1D flow problems are considered: a micro Fourier flow problem tests the energy coupling procedure of the method, and a high-speed micro Couette flow problem demonstrates the full coupling algorithm. In general, the method's accuracy is found to depend on the arrangement of the micro elements - with sufficient micro resolution, good agreement with the equivalent full DSMC simulations can be obtained. Although the hybrid method offers no computational speed-up over the full DSMC simulations for several of these 1D test cases and only modest speed-ups for the others, both of these 1D ow problems are simulated only to validate the coupling strategy of the method. Considerable speed-ups are offered by the method when simulating a larger and more realistic flow problem: a microchannel with a high-aspect-ratio cross-section acts as a representative geometry for modelling a gas flow through a narrow microscale crack. While the limitations of existing hybrid methods preclude their use for this type of high-aspect-ratio geometry, the new hybrid method is able to model this problem under isothermal and non-isothermal conditions. The implementation of the method is simplified to 2D by assuming that the flow variation in the streamwise direction is negligible, i.e. the method is applied to the microchannel cross-section only. Accurate predictions of the mass flow rate and the streamwise velocity field are obtained for a number of test cases; accurate predictions of the temperature field are also obtained when there is a temperature difference between the bounding walls.
Download or read book Proceedings of the International Field Exploration and Development Conference 2017 written by Zhan Qu and published by Springer. This book was released on 2018-07-11 with total page 1921 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents selected papers from the 7th International Field Exploration and Development Conference (IFEDC 2017), which focus on upstream technologies used in oil & gas development, the principles of the process, and various design technologies. The conference not only provides a platform for exchanging lessons learned, but also promotes the development of scientific research in oil & gas exploration and production. The book will benefit a broad readership, including industry experts, researchers, educators, senior engineers and managers.
Download or read book Computational and Experimental Simulations in Engineering written by Kun Zhou and published by Springer Nature. This book was released on with total page 1074 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Bridging Scales in Modelling and Simulation of Non Reacting and Reacting Flows Part II written by and published by Academic Press. This book was released on 2018-04-24 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bridging Scales in Modelling and Simulation of Reacting Flows, Part B, Volume 53, presents key methods used to bridge scales in the simulation of reacting multiphase flows. It looks at the different aspects of such flows (transport phenomena, reactions) and includes illustrations of the methods on a variety of applications, along with the contribution of key groups in the field. Sections in this new release include multi-scale methods for fluidized bed reactors, a discussion of advances in coarse-grained discrete particle methods with industrial applications, and spatial filtering for scale bridging and its application to transport in dense bidisperse particle beds, and more. - Contains reviews by leading authorities in their respective areas - Presents up-to-date reviews of the latest techniques in the modeling of catalytic processes - Includes a broad mix of US and European authors, as well as academic, industrial and research institute perspectives - Provides discussions on the connections between computation and experimental methods
Download or read book A Unified Computational Fluid Dynamics Framework from Rarefied to Continuum Regimes written by Kun Xu and published by Cambridge University Press. This book was released on 2021-06-10 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Element presents a unified computational fluid dynamics framework from rarefied to continuum regimes. The framework is based on the direct modelling of flow physics in a discretized space. The mesh size and time step are used as modelling scales in the construction of discretized governing equations. With the variation-of-cell Knudsen number, continuous modelling equations in different regimes have been obtained, and the Boltzmann and Navier-Stokes equations become two limiting equations in the kinetic and hydrodynamic scales. The unified algorithms include the discrete velocity method (DVM)–based unified gas-kinetic scheme (UGKS), the particlebased unified gas-kinetic particle method (UGKP), and the wave and particle–based unified gas-kinetic wave-particle method (UGKWP). The UGKWP is a multi-scale method with the particle for non-equilibrium transport and wave for equilibrium evolution. The particle dynamics in the rarefied regime and the hydrodynamic flow solver in the continuum regime have been unified according to the cell's Knudsen number.
Download or read book MEMS written by Mohamed Gad-el-Hak and published by CRC Press. This book was released on 2005-11-29 with total page 494 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thoroughly revised and updated, the new edition of the best-selling MEMS Handbook is now presented as a three-volume set that offers state-of-the-art coverage of microelectromechanical systems. The first volume, MEMS: Introduction and Fundamentals builds the required background and explores various physical considerations of MEMS. Topics include scaling, simulation models, the basics of control theory, and the physics of materials flow, thin liquid films, and bubble/drop transport. New chapters in this edition address lattice Boltzmann simulations and microscale hydrodynamics. Standing well on its own, this books builds an outstanding foundation for further exploration of MEMS and their applications.
Download or read book Nonequilibrium Gas Dynamics and Molecular Simulation written by Iain D. Boyd and published by Cambridge University Press. This book was released on 2017-03-23 with total page 383 pages. Available in PDF, EPUB and Kindle. Book excerpt: This current and comprehensive book provides an updated treatment of molecular gas dynamics topics for aerospace engineers, or anyone researching high-temperature gas flows for hypersonic vehicles and propulsion systems. It demonstrates how the areas of quantum mechanics, kinetic theory, and statistical mechanics can combine in order to facilitate the study of nonequilibrium processes of internal energy relaxation and chemistry. All of these theoretical ideas are used to explain the direct simulation Monte Carlo (DSMC) method, a numerical technique based on molecular simulation. Because this text provides comprehensive coverage of the physical models available for use in the DSMC method, in addition to the equations and algorithms required to implement the DSMC numerical method, readers will learn to solve nonequilibrium flow problems and perform computer simulations, and obtain a more complete understanding of various physical modeling options for DSMC than is available in other texts.
Download or read book The MEMS Handbook written by Mohamed Gad-el-Hak and published by CRC Press. This book was released on 2001-09-27 with total page 1386 pages. Available in PDF, EPUB and Kindle. Book excerpt: The revolution is well underway. Our understanding and utilization of microelectromechanical systems (MEMS) are growing at an explosive rate with a worldwide market approaching billions of dollars. In time, microdevices will fill the niches of our lives as pervasively as electronics do right now. But if these miniature devices are to fulfill their mammoth potential, today's engineers need a thorough grounding in the underlying physics, modeling techniques, fabrication methods, and materials of MEMS. The MEMS Handbook delivers all of this and more. Its team of authors-unsurpassed in their experience and standing in the scientific community- explore various aspects of MEMS: their design, fabrication, and applications as well as the physical modeling of their operations. Designed for maximum readability without compromising rigor, it provides a current and essential overview of this fledgling discipline.
Download or read book Computational Fluid Dynamics 2004 written by Clinton Groth and published by Springer Science & Business Media. This book was released on 2006-09-27 with total page 853 pages. Available in PDF, EPUB and Kindle. Book excerpt: Those interested in state of the art in computational fluid dynamics will find this publication a valuable source of reference. The contributions are drawn from The International Conference on Computational Fluid Dynamics (ICCFD) held in 2004. The conference is staged every two years and brings together physicists, mathematicians and engineers who review and share recent advances in mathematical and computational techniques for modeling fluid dynamics.
Download or read book Department of Housing and Urban Development independent agencies appropriations for 1989 written by United States. Congress. House. Committee on Appropriations. Subcommittee on HUD-Independent Agencies and published by . This book was released on 1988 with total page 1246 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Exploring Continuum Computational Models for Neutral Gas Flow in the JET Neutraliser written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Effective understanding of gas flow is important to ensure efficient operation of gas neutralizer systems such as those used at the Joint European Torus (JET), which form part of invaluable heating systems for nuclear fusion experiments. Computational fluid dynamics modelling of the neutral gas flow in the JET neutraliser has been undertaken, motivated by the shortfall in neutralisation efficiency and apparent loss of gas target observed in the JET neutraliser system. This has presented a challenging modelling endeavour due to the interaction of beam, background plasma and rarefied neutral gas. Utilising the continuum flow approximation, the Navier-Stokes and Augmented Burnett equations have been implemented and applied in conjunction with secondorder slip boundary conditions to form a gas solver accurate within the continuum-transition regime. Simulations in the presence of the ionic beam and background neutraliser plasma encountered during tokamak heating operations have been achieved via the development of a coupled beamplasma- gas solver. The gas flow governing equations have been supplemented by a series of source/sink terms for mass/energy that describe the complex web of interactions between the neutraliser constituents. The developed solver has been validated against experimental data, both in the absence and presence of beam. The design of future gas neutraliser systems has also been considered, with variation of several model and geometry parameters in order to better understand the loss of neutralisation efficiency and how future systems might be optimised. The neutraliser design for the forthcoming International Thermonuclear Experimental Reactor (ITER) has also been evaluated.
Download or read book Nonequilibrium Processes in the Planetary and Cometary Atmospheres Theory and Applications written by Mikhail Ya. Marov and published by Springer Science & Business Media. This book was released on 2001-11-30 with total page 308 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book reviews the approach to the kinetic simulation of nonequilib rium processes in the planetary atmospheres which the authors developed and dealt with since the 1970s. The results of this study, which are focused on the nonequilibrium collisional processes in the atmospheres of planets and comets, are thoroughly reviewed and discussed. Many specific problems of atmospheric modeling, involving numerical evaluation of aeronomic pro cesses, are addressed and compared with the available experimental data. The kinetic approach proved to be especially effective to model the in teraction of the incident shortwave solar radiation with the rarefied gas of planetary upper atmospheres. It involves various processes of photolysis, en ergetic electron impacts, and accompanying numerous chemical reactions, as well as processes occurring in the intermediate ("transition") zones of planetary and cometary gas envelopes. The underlying mathematical treat ment is based on the stochastic approach for the solution of the Boltzmann type equation and implies the development of the efficient algorithms for its computer simulation. Some results of this study were previously summa rized in the monograph issued in Russian (Marov et al. , 1990) and later in the review paper published in Space Science Reviews (Marov et al. , 1996). The basic principles of stochastic simulation were first developed in the field of rarefied gas dynamics and were successfully applied to the solution of some engineering problems of aerodynamics and heat transfer.
Download or read book Recent Advances in Theoretical Applied Computational and Experimental Mechanics written by B. N. Singh and published by Springer Nature. This book was released on 2020-04-03 with total page 454 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains selected papers presented at the 7th International Conference on Theoretical, Applied, Computational and Experimental Mechanics. The papers come from diverse disciplines, such as aerospace, civil, mechanical, and reliability engineering, physics, and navel architecture. The contents of this volume focus on different aspects of mechanics, namely, fluid mechanics, solid mechanics, flight mechanics, control, and propulsion. This volume will be of use to researchers interested in the study of mechanics across disciplines.
Download or read book Exploring Continuum Computational Models for Neutral Gas Flow in the JET Neutraliser written by Michael Porton and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Effective understanding of gas flow is important to ensure efficient operation of gas neutralizer systems such as those used at the Joint European Torus (JET), which form part of invaluableheating systems for nuclear fusion experiments. Computational fluid dynamics modelling of theneutral gas flow in the JET neutraliser has been undertaken, motivated by the shortfall in neutralisationefficiency and apparent loss of gas target observed in the JET neutraliser system. This haspresented a challenging modelling endeavour due to the interaction of beam, background plasmaand rarefied neutral gas. Utilising the continuum flow approximation, the Navier-Stokes andAugmented Burnett equations have been implemented and applied in conjunction with secondorderslip boundary conditions to form a gas solver accurate within the continuum-transitionregime. Simulations in the presence of the ionic beam and background neutraliser plasma encounteredduring tokamak heating operations have been achieved via the development of a coupled beamplasma-gas solver. The gas flow governing equations have been supplemented by a series ofsource/sink terms for mass/energy that describe the complex web of interactions between theneutraliser constituents. The developed solver has been validated against experimental data, both in the absence andpresence of beam. The design of future gas neutraliser systems has also been considered, withvariation of several model and geometry parameters in order to better understand the loss ofneutralisation efficiency and how future systems might be optimised. The neutraliser design forthe forthcoming International Thermonuclear Experimental Reactor (ITER) has also been evaluated.
Download or read book Rarefied Gas Dynamics written by M. Capitelli and published by American Institute of Physics. This book was released on 2005-06-21 with total page 1386 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book contains papers presented at the 24th International Symposium on Rarefied Gas Dynamics, a conference that is recognized as the principal forum for the presentation of recent advances in the field of rarefied gas dynamics. The topics include fundamental aspects of Boltzmann and related equations, transport theory, Monte Carlo methods, kinetic theory, gas phase molecular collision dynamics, gas surface interaction, state to state kinetics, rarefied plasmas, and non-equilibrium plasma kinetics. Applications in the fields of internal flows, vacuum systems, rarefied jets, plumes, molecular beams, scamjets and hypersonics, microflows, granular gases, electrical thrusters are discussed. Researchers in the fields of mathematics, physics, chemistry and engineering can strongly benefit from the interdisciplinary nature of the book.
