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Resolvent Analysis Techniques For Turbulent Flows
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Book Synopsis Resolvent Analysis Techniques for Turbulent Flows by : Dylan House
Download or read book Resolvent Analysis Techniques for Turbulent Flows written by Dylan House and published by . This book was released on 2021 with total page 57 pages. Available in PDF, EPUB and Kindle. Book excerpt: Resolvent analysis allows for the extraction of the dominant input-output behavior of a fluid flow near a mean state, which can be used to advise potential applications to flow control. A significant hurdle in the adoption of resolvent analysis is the singular value decomposition (SVD) of the large linear operators involved. A matrix sketching algorithm is used to extract the primary forcing and response modes, with their associated gain. The formulation of an iterative algorithm is shown to be able to calculate the SVD of the resolvent operator with greater accuracy. The sources of error due to the selection of a test vector are discussed and it is shown that an accurate calculation of the forcing and response modes can be obtained by utilizing a test vector corresponding to a single point. The strength of this algorithm is shown by calculating the resolvent modes for a flow over a NACA 0012 airfoil at a Reynolds number of 23,000. This method is shown to converge for an arbitrary selection of test vector, obtaining results in agreement with past studies of this flow. This method is used to perform windowed resolvent analysis on a two-dimensional turbulent flow of over a Honda sports utility vehicle (SUV) at $Re\approx 2.5\times 10^4$ to propose a flow control strategy for drag reduction. The force characteristics of the SUV are highly dependent on the wake structures and large structures in the wake region near the rear end of the vehicle are responsible for increase in drag of an SUV. We characterize the flow physics and modal analysis of the shear layer on the roof and the role of shear layer physics leading to the large structures in the wake dynamics. A moving window approach to investigate the windowed response modes of the resolvent operator over the roof of SUV is performed. The location of maximum gain shifts to the rear of the car as the spanwise wavenumer is reduced indicating the transition from small structures in the shear layer to large structures in the wake region. We use a body constrained window for forcing modes to investigate the optimum location of forcing to achieve desired response along the roof of the vehicle. An optimal forcing strategy about the placement of actuators and the frequency and direction of forcing is suggested after investigating the forcing modes at different frequencies and wave numbers.
Book Synopsis Turbulent Flow by : Peter S. Bernard
Download or read book Turbulent Flow written by Peter S. Bernard and published by John Wiley & Sons. This book was released on 2002-08-19 with total page 516 pages. Available in PDF, EPUB and Kindle. Book excerpt: Provides unique coverage of the prediction and experimentation necessary for making predictions. * Covers computational fluid dynamics and its relationship to direct numerical simulation used throughout the industry. * Covers vortex methods developed to calculate and evaluate turbulent flows. * Includes chapters on the state-of-the-art applications of research such as control of turbulence.
Book Synopsis Stability and Transition in Shear Flows by : Peter J. Schmid
Download or read book Stability and Transition in Shear Flows written by Peter J. Schmid and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 561 pages. Available in PDF, EPUB and Kindle. Book excerpt: A detailed look at some of the more modern issues of hydrodynamic stability, including transient growth, eigenvalue spectra, secondary instability. It presents analytical results and numerical simulations, linear and selected nonlinear stability methods. By including classical results as well as recent developments in the field of hydrodynamic stability and transition, the book can be used as a textbook for an introductory, graduate-level course in stability theory or for a special-topics fluids course. It is equally of value as a reference for researchers in the field of hydrodynamic stability theory or with an interest in recent developments in fluid dynamics. Stability theory has seen a rapid development over the past decade, this book includes such new developments as direct numerical simulations of transition to turbulence and linear analysis based on the initial-value problem.
Book Synopsis Liutex and Its Applications in Turbulence Research by : Chaoqun Liu
Download or read book Liutex and Its Applications in Turbulence Research written by Chaoqun Liu and published by Academic Press. This book was released on 2020-10-29 with total page 458 pages. Available in PDF, EPUB and Kindle. Book excerpt: Liutex and Its Applications in Turbulence Research reviews the history of vortex definition, provides an accurate mathematical definition of vortices, and explains their applications in flow transition, turbulent flow, flow control, and turbulent flow experiments. The book explains the term "Rortex" as a mathematically defined rigid rotation of fluids or vortex, which could help solve many longstanding problems in turbulence research. The accurate mathematical definition of the vortex is important in a range of industrial contexts, including aerospace, turbine machinery, combustion, and electronic cooling systems, so there are many areas of research that can benefit from the innovations described here. This book provides a thorough survey of the latest research in generalized and flow-thermal, unified, law-of-the-wall for wall-bounded turbulence. Important theory and methodologies used for developing these laws are described in detail, including: the classification of the conventional turbulent boundary layer concept based on proper velocity scaling; the methodology for identification of the scales of velocity, temperature, and length needed to establish the law; and the discovery, proof, and strict validations of the laws, with both Reynolds and Prandtl number independency properties using DNS data. The establishment of these statistical laws is important to modern fluid mechanics and heat transfer research, and greatly expands our understanding of wall-bounded turbulence. Provides an accurate mathematical definition of vortices Provides a thorough survey of the latest research in generalized and flow-thermal, unified, law-of-the-wall for wall-bounded turbulence Explains the term “Rortex as a mathematically defined rigid rotation of fluids or vortex Covers the statistical laws important to modern fluid mechanics and heat transfer research, and greatly expands our understanding of wall-bounded turbulence
Book Synopsis Viscous Drag Reduction in Boundary Layers by :
Download or read book Viscous Drag Reduction in Boundary Layers written by and published by AIAA. This book was released on 1990 with total page 542 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Advanced Approaches in Turbulence by : Paul Durbin
Download or read book Advanced Approaches in Turbulence written by Paul Durbin and published by Elsevier. This book was released on 2021-07-24 with total page 554 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advanced Approaches in Turbulence: Theory, Modeling, Simulation and Data Analysis for Turbulent Flows focuses on the updated theory, simulation and data analysis of turbulence dealing mainly with turbulence modeling instead of the physics of turbulence. Beginning with the basics of turbulence, the book discusses closure modeling, direct simulation, large eddy simulation and hybrid simulation. The book also covers the entire spectrum of turbulence models for both single-phase and multi-phase flows, as well as turbulence in compressible flow. Turbulence modeling is very extensive and continuously updated with new achievements and improvements of the models. Modern advances in computer speed offer the potential for elaborate numerical analysis of turbulent fluid flow while advances in instrumentation are creating large amounts of data. This book covers these topics in great detail. - Covers the fundamentals of turbulence updated with recent developments - Focuses on hybrid methods such as DES and wall-modeled LES - Gives an updated treatment of numerical simulation and data analysis
Download or read book Turbulent Flows written by G. Biswas and published by Narosa Publishing House. This book was released on 2002 with total page 476 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book allows readers to tackle the challenges of turbulent flow problems with confidence. It covers the fundamentals of turbulence, various modeling approaches, and experimental studies. The fundamentals section includes isotropic turbulence and anistropic turbulence, turbulent flow dynamics, free shear layers, turbulent boundary layers and plumes. The modeling section focuses on topics such as eddy viscosity models, standard K-E Models, Direct Numerical Stimulation, Large Eddy Simulation, and their applications. The measurement of turbulent fluctuations experiments in isothermal and stratified turbulent flows are explored in the experimental methods section. Special topics include modeling of near wall turbulent flows, compressible turbulent flows, and more.
Book Synopsis Direct Numerical Simulations, Resolvent Analysis, and Flow Control of Laminar Post-stall Wakes Around Finite Tapered Swept Wings by : Jean Helder Marques Ribeiro
Download or read book Direct Numerical Simulations, Resolvent Analysis, and Flow Control of Laminar Post-stall Wakes Around Finite Tapered Swept Wings written by Jean Helder Marques Ribeiro and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: External flows over wings is a traditional flow of interest in aerodynamics. Over the last century, research efforts were dedicated to studying the wake patterns that form in the flows around finite wings. Among others, we can pinpoint the wing tip vortex, the separation region that develops under adverse pressure gradient, and the coherent vortical structures. Thanks to these past efforts, we were able to significantly extend our knowledge in aerodynamics, which paved the way for an impressive evolution of aircraft designs in the last century. Over the years, commercial flight became an ordinary asset in our society. More recently, small and micro air vehicles have also reached the market, being operated by individuals who hold no necessary knowledge of the complexity of the Navier-Stokes equations. The advanced knowledge currently held on flight physics has played a fundamental role in the development of aircraft designs, however, there is still room for improvement. In post-stall flow conditions, the aerodynamic performance of the wing decays considerably, making it challenging to sustain flight at high incidence angles. To enable flight in such flow conditions, it is important to develop physics-based flow control strategies capable of improving the overall aerodynamic performance of the wing and its flight stability. The main implications are reduced fuel (and energy) consumption during flight, increased aircraft range, improvements in safety and productivity of air travel, attenuation of the acoustic signature, as well as enabled capability of aircraft to fly in challenging external environments. Towards this goal, many studies have been performed to analyze and control flows over airfoils in spanwise periodic configurations. These may also be called infinite-span wings. These studies were fundamental to revealing important aspects of flow physics. However, in reality, the flows around wings are three-dimensional (3-D). In addition, modern aircraft wings are usually tapered and swept. The 3-D vortex dynamics of flows over wings has a significant influence on aircraft design, by reducing the overall lift, generating induced drag, and increasing flow unsteadiness. Thus, it is important to develop strategies to control the vortex dynamics that encompass the knowledge of the 3-D characteristics of the flow over finite, swept, and tapered wings. Especially for post-stall flow conditions, the wake dynamics around tapered swept wings is largely unexplored. It is still a challenge to understand how the wing geometry relates to the vortex formation for different aspect and taper ratios, as well as angles of attack and sweep. To design control strategies to improve aerodynamic performance for finite, swept, and tapered wings, we must go beyond the sole characterization of flow structures. In fact, the identification of perturbation dynamics is called for to modify the flow field. Three-dimensional flow control is challenging due to the high-dimensional and nonlinear nature of the flow dynamics of the wakes. Thus, it is necessary to find an appropriate actuation setup for the problem that can alter the base flow behavior. This effort can be guided by modal analysis methods. In our work, we have used resolvent analysis, a method based on the singular value decomposition (SVD) of the resolvent, which is a linear operator constructed using the Navier-Stokes equations linearized with respect to the base flow. For unsteady flows, the statistically converged time-averaged flow field is used as a base flow to construct the resolvent operator. The strength of the resolvent operator through this approach is the capability to find optimal forcing modes which amplify outputs in the flow field and give insights into the perturbed flow through the spatial response modes. The challenge within resolvent analysis is the SVD computation for large-scale resolvent operators that are generated for high-dimensional flow fields, such as three-dimensional and turbulent flows. By taking advantage of low-rank approximation of the resolvent operator, recent developments using randomized numerical linear algebra have accelerated the computation of the dominant resolvent modes. With reduced computational costs, these efforts have enabled the use of resolvent analysis in turbulent flows over spanwise periodic airfoils and expanded its applicability to triglobal problems and higher Reynolds number flows. With the randomized algorithm, we can use resolvent analysis to uncover the dynamics of 3-D flows over finite, swept, and tapered wings, supporting flow control efforts to improve their overall aerodynamic performance. The present study has shown how to develop a 3-D resolvent-based flow control over finite wings. We initiate by studying flows over finite wings and the effects of wing sweep and taper on the post-stall wake dynamics through direct numerical simulations (DNS). We consider laminar flows at chord-based Reynolds numbers of 400 and 600 with weak compressible effects at a freestream Mach number 0.1. The flows are studied around wings at angles of attack between 14 and 30 degrees with semi aspect ratios ranging from 1 to 4, sweep angles up to 50 degrees, and taper ratios from 0.27 to 1. Following a comprehensive characterization of the wake dynamics through DNS results, we extend our knowledge of the dynamics of flow perturbations by analyzing the triglobal resolvent modes. Through the identification of the optimal harmonic perturbations that can be amplified in the flow field, we develop 3-D active flow control that is shown to significantly modify the wake structures around the wings. This comprehensive investigation provides novel and unique insights that reveal the flow structures that can be amplified in the wake and modify their dynamics in post-stall flow conditions.
Book Synopsis New Results in Numerical and Experimental Fluid Mechanics XII by : Andreas Dillmann
Download or read book New Results in Numerical and Experimental Fluid Mechanics XII written by Andreas Dillmann and published by Springer Nature. This book was released on 2019-09-26 with total page 867 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book gathers contributions to the 21st biannual symposium of the German Aerospace Aerodynamics Association (STAB) and the German Society for Aeronautics and Astronautics (DGLR). The individual chapters reflect ongoing research conducted by the STAB members in the field of numerical and experimental fluid mechanics and aerodynamics, mainly for (but not limited to) aerospace applications, and cover both nationally and EC-funded projects. Special emphasis is given to collaborative research projects conducted by German scientists and engineers from universities, research-establishments and industries. By addressing a number of cutting-edge applications, together with the relevant physical and mathematics fundamentals, the book provides readers with a comprehensive overview of the current research work in the field. The book’s primary emphasis is on aerodynamic research in aeronautics and astronautics, and in ground transportation and energy as well.
Book Synopsis Turbulence, Coherent Structures, Dynamical Systems and Symmetry by : Philip Holmes
Download or read book Turbulence, Coherent Structures, Dynamical Systems and Symmetry written by Philip Holmes and published by Cambridge University Press. This book was released on 2012-02-23 with total page 403 pages. Available in PDF, EPUB and Kindle. Book excerpt: Describes methods revealing the structures and dynamics of turbulence for engineering, physical science and mathematics researchers working in fluid dynamics.
Book Synopsis Numerical Prediction of Flow, Heat Transfer, Turbulence and Combustion by : D. Brian Spalding
Download or read book Numerical Prediction of Flow, Heat Transfer, Turbulence and Combustion written by D. Brian Spalding and published by Elsevier. This book was released on 2015-07-14 with total page 445 pages. Available in PDF, EPUB and Kindle. Book excerpt: Numerical Prediction of Flow, Heat Transfer, Turbulence and Combustion: Selected Works of Professor D. Brian Spalding focuses on the many contributions of Professor Spalding on thermodynamics. This compilation of his works is done to honor the professor on the occasion of his 60th birthday. Relatively, the works contained in this book are selected to highlight the genius of Professor Spalding in this field of interest. The book presents various research on combustion, heat transfer, turbulence, and flows. His thinking on separated flows paved the way for the multi-dimensional modeling of turbulence. Arguments on the universality of the models of turbulence and the problems that are associated with combustion engineering are clarified. The text notes the importance of combustion science as well as the problems associated with it. Mathematical computations are also presented in determining turbulent flows in different environments, including on curved pipes, curved ducts, and rotating ducts. These calculations are presented to further strengthen the claims of Professor Spalding in this discipline. The book is a great find for those who are interested in studying thermodynamics.
Book Synopsis Computational Fluid Dynamics by : Takeo Kajishima
Download or read book Computational Fluid Dynamics written by Takeo Kajishima and published by Springer. This book was released on 2016-10-01 with total page 364 pages. Available in PDF, EPUB and Kindle. Book excerpt: This textbook presents numerical solution techniques for incompressible turbulent flows that occur in a variety of scientific and engineering settings including aerodynamics of ground-based vehicles and low-speed aircraft, fluid flows in energy systems, atmospheric flows, and biological flows. This book encompasses fluid mechanics, partial differential equations, numerical methods, and turbulence models, and emphasizes the foundation on how the governing partial differential equations for incompressible fluid flow can be solved numerically in an accurate and efficient manner. Extensive discussions on incompressible flow solvers and turbulence modeling are also offered. This text is an ideal instructional resource and reference for students, research scientists, and professional engineers interested in analyzing fluid flows using numerical simulations for fundamental research and industrial applications.
Book Synopsis Inequalities for Differential and Integral Equations by :
Download or read book Inequalities for Differential and Integral Equations written by and published by Elsevier. This book was released on 1997-11-12 with total page 623 pages. Available in PDF, EPUB and Kindle. Book excerpt: Inequalities for Differential and Integral Equations has long been needed; it contains material which is hard to find in other books. Written by a major contributor to the field, this comprehensive resource contains many inequalities which have only recently appeared in the literature and which can be used as powerful tools in the development of applications in the theory of new classes of differential and integral equations. For researchers working in this area, it will be a valuable source of reference and inspiration. It could also be used as the text for an advanced graduate course. - Covers a variety of linear and nonlinear inequalities which find widespread applications in the theory of various classes of differential and integral equations - Contains many inequalities which have only recently appeared in literature and cannot yet be found in other books - Provides a valuable reference to engineers and graduate students
Book Synopsis Spectra and Pseudospectra by : Lloyd N. Trefethen
Download or read book Spectra and Pseudospectra written by Lloyd N. Trefethen and published by Princeton University Press. This book was released on 2005-08-07 with total page 634 pages. Available in PDF, EPUB and Kindle. Book excerpt: Pure and applied mathematicians, physicists, scientists, and engineers use matrices and operators and their eigenvalues in quantum mechanics, fluid mechanics, structural analysis, acoustics, ecology, numerical analysis, and many other areas. However, in some applications the usual analysis based on eigenvalues fails. For example, eigenvalues are often ineffective for analyzing dynamical systems such as fluid flow, Markov chains, ecological models, and matrix iterations. That's where this book comes in. This is the authoritative work on nonnormal matrices and operators, written by the authorities who made them famous. Each of the sixty sections is written as a self-contained essay. Each document is a lavishly illustrated introductory survey of its topic, complete with beautiful numerical experiments and all the right references. The breadth of included topics and the numerous applications that provide links between fields will make this an essential reference in mathematics and related sciences.
Book Synopsis Turbulent Fluid Flow by : Peter S. Bernard
Download or read book Turbulent Fluid Flow written by Peter S. Bernard and published by John Wiley & Sons. This book was released on 2019-03-11 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt: A guide to the essential information needed to model and compute turbulent flows and interpret experiments and numerical simulations Turbulent Fluid Flow offers an authoritative resource to the theories and models encountered in the field of turbulent flow. In this book, the author – a noted expert on the subject – creates a complete picture of the essential information needed for engineers and scientists to carry out turbulent flow studies. This important guide puts the focus on the essential aspects of the subject – including modeling, simulation and the interpretation of experimental data - that fit into the basic needs of engineers that work with turbulent flows in technological design and innovation. Turbulent Fluid Flow offers the basic information that underpins the most recent models and techniques that are currently used to solve turbulent flow challenges. The book provides careful explanations, many supporting figures and detailed mathematical calculations that enable the reader to derive a clear understanding of turbulent fluid flow. This vital resource: Offers a clear explanation to the models and techniques currently used to solve turbulent flow problems Provides an up-to-date account of recent experimental and numerical studies probing the physics of canonical turbulent flows Gives a self-contained treatment of the essential topics in the field of turbulence Puts the focus on the connection between the subject matter and the goals of fluids engineering Comes with a detailed syllabus and a solutions manual containing MATLAB codes, available on a password-protected companion website Written for fluids engineers, physicists, applied mathematicians and graduate students in mechanical, aerospace and civil engineering, Turbulent Fluid Flow contains an authoritative resource to the information needed to interpret experiments and carry out turbulent flow studies.
Book Synopsis Mathematics of Two-Dimensional Turbulence by : Sergei Kuksin
Download or read book Mathematics of Two-Dimensional Turbulence written by Sergei Kuksin and published by Cambridge University Press. This book was released on 2012-09-20 with total page 337 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is dedicated to the mathematical study of two-dimensional statistical hydrodynamics and turbulence, described by the 2D Navier–Stokes system with a random force. The authors' main goal is to justify the statistical properties of a fluid's velocity field u(t,x) that physicists assume in their work. They rigorously prove that u(t,x) converges, as time grows, to a statistical equilibrium, independent of initial data. They use this to study ergodic properties of u(t,x) – proving, in particular, that observables f(u(t,.)) satisfy the strong law of large numbers and central limit theorem. They also discuss the inviscid limit when viscosity goes to zero, normalising the force so that the energy of solutions stays constant, while their Reynolds numbers grow to infinity. They show that then the statistical equilibria converge to invariant measures of the 2D Euler equation and study these measures. The methods apply to other nonlinear PDEs perturbed by random forces.
Book Synopsis Engineering Calculation Methods for Turbulent Flow by : Peter Bradshaw
Download or read book Engineering Calculation Methods for Turbulent Flow written by Peter Bradshaw and published by . This book was released on 1981 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt:
