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Development And Application Of Rotation And Curvature Correction To Wray Agarwal Turbulence Model
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Book Synopsis Development and Application of Rotation and Curvature Correction to Wray-Agarwal Turbulence Model by : Xiao Zhang (Mechanical engineer)
Download or read book Development and Application of Rotation and Curvature Correction to Wray-Agarwal Turbulence Model written by Xiao Zhang (Mechanical engineer) and published by . This book was released on 2018 with total page 99 pages. Available in PDF, EPUB and Kindle. Book excerpt: Computational Fluid Dynamics (CFD) is increasingly playing a significant role in the analysis and design of aircrafts, turbomachines, automobiles, and in many other industrial applications. In majority of the applications, the fluid flow is generally turbulent. The accurate prediction of turbulent flows to date remains a challenging problem in CFD. In almost all industrial applications, Reynolds-Averaged Navier-Stokes (RANS) equations in conjunction with a turbulence model are employed for simulation and prediction of turbulent flows. Currently the one-equation (namely the Spalart-Allmaras (SA) and Wray-Agarwal (WA) and two-equation (namely the k-[epsilon] and Shear Stress Transport k-[omega]) turbulence models remain the most widely used models in industry. However, improvements and new developments are needed to improve the accuracy of the turbulence models for wall bounded flows with separation in the presence of adverse pressure gradients, and for flows with rotation and curvature (RC) such as those encountered in turbomachinery, centrifugal pumps and the rotating machinery in other industrial devices. The goal of this research is to enable the eddy-viscosity type turbulence models to accurately account for the rotation and curvature effects. To date, there have been two approaches for inclusion of RC effects in turbulence models, which can be categorized as the "Modified Coefficients Approach" which parameterizes the model coefficients such that the growth rate of turbulent kinetic energy is either suppressed or enhanced depending upon the effect of system rotation and streamline curvature on the pressure gradient in the flow and the "Bifurcation Approach" which parameterizes the eddy-viscosity coefficient such that the equilibrium solution bifurcates from the main branch to decaying solution branches. In this research, the uncertainty quantification (UQ) is applied to examine the sensitivity of RC correction coefficients and the coefficients are modified based on the UQ analysis to improve the model's behavior. Both these approaches are applied to the widely used turbulence models (SA, SST k-[omega] and WA) and they show some improvement in predictions of turbulent flow in all benchmark test cases considered, namely the flow in a 2D curved duct, flow in a 2D U-turn duct, fully developed turbulent flow in a 2D rotating channel, fully developed turbulent flow in a 2D rotating backward-facing step, flow in a rotating cavity, flow in a stationary and rotating serpentine channel, flow in a rotor-stator cavity and in a hydrocyclone as well as two wall-unbounded turbulent flow cases. All the simulations are conducted using the commercial software ANSYS Fluent and the open source CFD software OpenFOAM. The success of this research should enhance the ability of the RANS modeling for more accurate prediction of complex turbulent flows with rotation and curvature effects. In addition to the RANS modeling of RC effects, a new DES model incorporating the WA2017m-RC turbulence model (referred to as the WA2017m-RC-DES model) is developed and validated against experimental and DNS data. Further improvements are obtained with the DES model in some test cases.
Book Synopsis Development of a One-equation Eddy Viscosity Turbulence Model for Application to Complex Turbulent Flows by : Timothy J. Wray
Download or read book Development of a One-equation Eddy Viscosity Turbulence Model for Application to Complex Turbulent Flows written by Timothy J. Wray and published by . This book was released on 2016 with total page 139 pages. Available in PDF, EPUB and Kindle. Book excerpt: Computational fluid dynamics (CFD) is routinely used in performance prediction and design of aircraft, turbomachinery, automobiles, and in many other industrial applications. Despite its wide range of use, deficiencies in its prediction accuracy still exist. One critical weakness is the accurate simulation of complex turbulent flows using the Reynolds-Averaged Navier-Stokes equations in conjunction with a turbulence model. The goal of this research has been to develop an eddy viscosity type turbulence model to increase the accuracy of flow simulations for mildly separated flows, flows with rotation and curvature effects, and flows with surface roughness. It is accomplished by developing a new zonal one-equation turbulence model which relies heavily on the flow physics; it is now known in the literature as the Wray-Agarwal one-equation turbulence model. The effectiveness of the new model is demonstrated by comparing its results with those obtained by the industry standard one-equation Spalart-Allmaras model and two-equation Shear-Stress-Transport k -- [omega] model and experimental data. Results for subsonic, transonic, and supersonic flows in and about complex geometries are presented. It is demonstrated that the Wray-Agarwal model can provide the industry and CFD researchers an accurate, efficient, and reliable turbulence model for the computation of a large class of complex turbulent flows.
Book Synopsis Development and Application of Hybrid Wray-Agarwal Turbulence Model and Large-eddy Simulation by : Xu Han (Mechanical engineer)
Download or read book Development and Application of Hybrid Wray-Agarwal Turbulence Model and Large-eddy Simulation written by Xu Han (Mechanical engineer) and published by . This book was released on 2018 with total page 101 pages. Available in PDF, EPUB and Kindle. Book excerpt: Rapid development in computing power in past five decades along with the development and progress in building blocks of Computational Fluid Dynamics (CFD) technology has made CFD an indispensable tool for modern engineering analysis and design of fluid-based products and systems. For CFD analysis, Reynolds-Averaged Navier-Stokes (RANS) equations are currently the most widely used fluid equations in the industry. RANS methods require modeling of turbulence effect (i.e. turbulence modeling) based on empirical relations and therefore often produce low accuracy results for many flows. In recent years, the Large Eddy Simulation (LES) approach has been developed which has shown promise of achieving higher accuracy, however it is computationally very intensive and therefore has remained limited to computing relatively simple flows from low to moderate Reynolds numbers. As a result, a hybrid technique called Detached Eddy Simulation (DES) has been proposed in recent years. This technique has shown improved accuracy and computational efficiency for solution of wide variety of complex turbulent flows. The goal of this dissertation has been to develop a DES model based on a recently proposed very promising RANS model, known as the 'Wray-Agarwal (WA)' model and the LES. Decaying Isotropic Turbulence (DIT) case is computed to determine the coefficient in the DES model by matching its energy spectrum with the Kolmogorov spectrum. The new WA-DES model (DES model based on WA model) is applied to compute a wide variety of wall bounded separated flows to assess it accuracy and computational efficiency compared to the widely used RANS turbulence models in the industry, namely the Spalart-Allmaras (SA) and SST k-[omega] models. Improved Delayed-Detached Eddy Simulation (IDDES) and Elliptic Blending are also considered as further refinements of WA model to improve its accuracy.
Book Synopsis Development and Analysis of Turbulence Models for Flows with Strong Curvature and Rotation by : Olof Grundestam
Download or read book Development and Analysis of Turbulence Models for Flows with Strong Curvature and Rotation written by Olof Grundestam and published by . This book was released on 2004 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis An Assessment of Rotation and Curvature Correction for One- and Two-equation Turbulence Models for Compressible Impinging Jet Flows by : M. Mani
Download or read book An Assessment of Rotation and Curvature Correction for One- and Two-equation Turbulence Models for Compressible Impinging Jet Flows written by M. Mani and published by . This book was released on 2000 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Development and Application of Quadratic Constitutive Relation and Transitional Crossflow Effects in the Wray-Agarwal Turbulence Model by : Hakop J. Nagapetyan
Download or read book Development and Application of Quadratic Constitutive Relation and Transitional Crossflow Effects in the Wray-Agarwal Turbulence Model written by Hakop J. Nagapetyan and published by . This book was released on 2018 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt: Computational Fluid Dynamics (CFD) has now become an almost indispensable tool for modern engineering analysis of fluid flow over aircrafts, turbomachinery, automobiles, and many other industrial applications. Accurate prediction of turbulent flows remains a challenging problem. The most popular approach for simulating turbulent flows in complex industrial applications is based on the solution of the Reynolds-Averaged Navier-Stokes (RANS) equations. RANS equations introduce the so called "Reynolds or turbulent stresses" which are generally modeled using the Boussinesq approximation known as "Turbulence modeling." Despite their development over a century, the turbulence models used with RANS equations still need much improvement. The first part of this research introduces the Quadratic Constitutive Relations (QCR), which is a nonlinear approach to approximating the turbulent stresses in eddy-viscosity class of turbulence models. In Boussinesq approximation, turbulent stresses are assumed to be linearly proportional to the strain with eddy viscosity being the proportionality constant. In recent years it has been found that linear eddy viscosity models are not accurate for prediction of vortical flows and wall bounded flows with mild separation with regions of recirculating flows. Such flows occur in junctions of aerodynamic surfaces e.g. the wing-body junction and in inlets and ducts with corners. The accurate prediction of these flows is needed for design improvements and better product performance. To remedy some of the shortcomings of the linear eddy-viscosity models, the Quadratic Constitutive Relation (QCR) for eddy viscosity is investigated to test its capability for predicting non-equilibrium turbulence effects. QCR is implemented in Spalart-Allmaras (SA), SST k-[omega] and Wray-Agarwal (WA) turbulence models and is applied to several applications involving large recirculating regions. It is demonstrated That QCR improves the results compared to linear eddy viscosity models. Another shortcoming of RANS models is their inability to accurately predict regions of transitional flow in a flow field. Many flow regions in industrial applications contain the transitional flow regime e.g. flows over aircraft wings and fuselages, past wind turbines and in gas turbines engines to name a few. The second part of this research has been on the development of a transitional model by suitably combining a correlation based intermittency-[gamma] equation with the WA turbulence model; this new model is designated as Wray-Agarwal-[gamma] (WA-[gamma]) transition model. The WA-[gamma] is extensively validated by computing a number of benchmark cases. The WA-[gamma] model is also extended to include the crossflow-instability induced transition which is a dominant mode of transition in flows involving three-dimensional boundary layers, e.g. flow past swept wings and ellipsoids. This modified WA-[gamma] model is validated using a benchmark test case for analyzing crossflow-induced transition.
Book Synopsis Development and Application of Elliptic Blending Lag K-[omega] SST Standard and Wall-distance-free Turbulence Model by : Wenjie Shang
Download or read book Development and Application of Elliptic Blending Lag K-[omega] SST Standard and Wall-distance-free Turbulence Model written by Wenjie Shang and published by . This book was released on 2020 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent decades, Computational Fluid Dynamics (CFD) has become the most widely used technology to understand the fundamental complex fluid dynamics of turbulent flows as well as for modeling of turbulent flows in industrial applications. In industrial applications, the widely used methodology is to solve Reynolds-Average Navier-Stokes Equations (RANS) equations in conjunction with a turbulence model since it strikes a balance between accuracy and computational cost compared to other high fidelity approaches namely the Large Eddy Simulation (LES) and Direct Numerical Simulation (DNS), There are a large number of turbulence models proposed in past five decades, majority of them are linear eddy viscosity models based on the Boussinesq's hypothesis. Among these, the one equation Spalart-Allmaras (SA) and Wray-Agarwal (WA) model and two equations k-[epsilon], k-[omega] and SST k-[omega] are most popular. Most of these models suffer from two drawbacks: (1) they have stress-strain misalignment in the near-wall region due to Boussinesq's hypothesis and (2) they contain wall distance as a parameter in the model which can introduce error in case of complex boundaries especially with the use of unstructured grids. The goal of this thesis is to address these two drawbacks in the standard k-[omega] SST model. The first issue is addressed by combining the k-[omega] SST model with the elliptic blending lag equation to correct the stress-strain misalignment and the second issue is addressed by developing a wall distance free k-[omega] SST model. The newly developed models are validated on several benchmark test cases given on NASA Turbulence Modeling Resource (TMR) website for both external and internal wall-bounded flows with small regions of separation. The computations show that both models can provide better agreement with the experimental data compared to the original k-[omega] SST mode
Book Synopsis Optimal Design and Efficiency Improvement of Fluid Machinery and Systems by : Ramesh K. Agarwal
Download or read book Optimal Design and Efficiency Improvement of Fluid Machinery and Systems written by Ramesh K. Agarwal and published by Frontiers Media SA. This book was released on 2023-07-19 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Shock Wave-Boundary-Layer Interactions by : Holger Babinsky
Download or read book Shock Wave-Boundary-Layer Interactions written by Holger Babinsky and published by Cambridge University Press. This book was released on 2011-09-12 with total page 481 pages. Available in PDF, EPUB and Kindle. Book excerpt: Shock wave-boundary-layer interaction (SBLI) is a fundamental phenomenon in gas dynamics that is observed in many practical situations, ranging from transonic aircraft wings to hypersonic vehicles and engines. SBLIs have the potential to pose serious problems in a flowfield; hence they often prove to be a critical - or even design limiting - issue for many aerospace applications. This is the first book devoted solely to a comprehensive, state-of-the-art explanation of this phenomenon. It includes a description of the basic fluid mechanics of SBLIs plus contributions from leading international experts who share their insight into their physics and the impact they have in practical flow situations. This book is for practitioners and graduate students in aerodynamics who wish to familiarize themselves with all aspects of SBLI flows. It is a valuable resource for specialists because it compiles experimental, computational and theoretical knowledge in one place.
Book Synopsis Boundary Layer Flows by : Vallampati Ramachandra Prasad
Download or read book Boundary Layer Flows written by Vallampati Ramachandra Prasad and published by BoD – Books on Demand. This book was released on 2020-01-22 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt: Written by experts in the field, this book, "Boundary Layer Flows - Theory, Applications, and Numerical Methods" provides readers with the opportunity to explore its theoretical and experimental studies and their importance to the nonlinear theory of boundary layer flows, the theory of heat and mass transfer, and the dynamics of fluid. With the theory's importance for a wide variety of applications, applied mathematicians, scientists, and engineers - especially those in fluid dynamics - along with engineers of aeronautics, will undoubtedly welcome this authoritative, up-to-date book.
Book Synopsis Modeling and Simulation of Turbulent Combustion by : Santanu De
Download or read book Modeling and Simulation of Turbulent Combustion written by Santanu De and published by Springer. This book was released on 2017-12-12 with total page 663 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents a comprehensive review of state-of-the-art models for turbulent combustion, with special emphasis on the theory, development and applications of combustion models in practical combustion systems. It simplifies the complex multi-scale and nonlinear interaction between chemistry and turbulence to allow a broader audience to understand the modeling and numerical simulations of turbulent combustion, which remains at the forefront of research due to its industrial relevance. Further, the book provides a holistic view by covering a diverse range of basic and advanced topics—from the fundamentals of turbulence–chemistry interactions, role of high-performance computing in combustion simulations, and optimization and reduction techniques for chemical kinetics, to state-of-the-art modeling strategies for turbulent premixed and nonpremixed combustion and their applications in engineering contexts.
Book Synopsis Low Reynolds Number by : Mustafa Serdar Genç
Download or read book Low Reynolds Number written by Mustafa Serdar Genç and published by BoD – Books on Demand. This book was released on 2012-04-04 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book reports the latest development and trends in the low Re number aerodynamics, transition from laminar to turbulence, unsteady low Reynolds number flows, experimental studies, numerical transition modelling, control of low Re number flows, and MAV wing aerodynamics. The contributors to each chapter are fluid mechanics and aerodynamics scientists and engineers with strong expertise in their respective fields. As a whole, the studies presented here reveal important new directions toward the realization of applications of MAV and wind turbine blades.
Book Synopsis Handbook of Technical Textiles by : A. Richard Horrocks
Download or read book Handbook of Technical Textiles written by A. Richard Horrocks and published by Woodhead Publishing. This book was released on 2015-12-01 with total page 396 pages. Available in PDF, EPUB and Kindle. Book excerpt: The second edition of Handbook of Technical Textiles, Volume 1: Technical Textile Processes provides readers with a comprehensive understanding of the latest advancements in technical textiles. With revised and updated coverage, including several new chapters, this volume reviews recent developments and technologies in the field, beginning with an overview of the technical textiles industry that includes coverage of technical fibers and yarns, weaving, spinning, knitting, and nonwoven production. Subsequent sections include discussions on finishing, coating, and the coloration of technical textiles. Provides a comprehensive handbook for all aspects of technical textiles Presents updated, detailed coverage of processes, fabric structure, and applications An ideal resource for those interested in high-performance textiles, textile processes, textile processing, and textile applications Contains contributions from many of the original, recognized experts from the first edition who update their respective chapters
Book Synopsis High Performance Computing in Science and Engineering ‘14 by : Wolfgang E. Nagel
Download or read book High Performance Computing in Science and Engineering ‘14 written by Wolfgang E. Nagel and published by Springer. This book was released on 2015-02-14 with total page 682 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the state-of-the-art in supercomputer simulation. It includes the latest findings from leading researchers using systems from the High Performance Computing Center Stuttgart (HLRS). The reports cover all fields of computational science and engineering ranging from CFD to computational physics and from chemistry to computer science with a special emphasis on industrially relevant applications. Presenting findings of one of Europe’s leading systems, this volume covers a wide variety of applications that deliver a high level of sustained performance. The book covers the main methods in high-performance computing. Its outstanding results in achieving the best performance for production codes are of particular interest for both scientists and engineers. The book comes with a wealth of color illustrations and tables of results.
Download or read book A Generalized Wall Function written by and published by . This book was released on 1999 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Digital Health written by Homero Rivas and published by Springer. This book was released on 2018-01-02 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents a comprehensive state-of the-art approach to digital health technologies and practices within the broad confines of healthcare practices. It provides a canvas to discuss emerging digital health solutions, propelled by the ubiquitous availability of miniaturized, personalized devices and affordable, easy to use wearable sensors, and innovative technologies like 3D printing, virtual and augmented reality and driverless robots and vehicles including drones. One of the most significant promises the digital health solutions hold is to keep us healthier for longer, even with limited resources, while truly scaling the delivery of healthcare. Digital Health: Scaling Healthcare to the World addresses the emerging trends and enabling technologies contributing to technological advances in healthcare practice in the 21st Century. These areas include generic topics such as mobile health and telemedicine, as well as specific concepts such as social media for health, wearables and quantified-self trends. Also covered are the psychological models leveraged in design of solutions to persuade us to follow some recommended actions, then the design and educational facets of the proposed innovations, as well as ethics, privacy, security, and liability aspects influencing its acceptance. Furthermore, sections on economic aspects of the proposed innovations are included, analyzing the potential business models and entrepreneurship opportunities in the domain.
Book Synopsis The Pluto System After New Horizons by : S. Alan Stern
Download or read book The Pluto System After New Horizons written by S. Alan Stern and published by University of Arizona Press. This book was released on 2021-08-10 with total page 684 pages. Available in PDF, EPUB and Kindle. Book excerpt: Once perceived as distant, cold, dark, and seemingly unknowable, Pluto had long been marked as the farthest and most unreachable frontier for solar system exploration. The Pluto System After New Horizons is the benchmark research compendium for synthesizing our understanding of the Pluto system. This volume reviews the work of researchers who have spent the last five years assimilating the data returned from New Horizons and the first full scientific synthesis of this fascinating system.
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