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Author : Xuanhong An
Publisher :
ISBN 13 :
Total Pages : 250 pages
Book Rating : 4.:/5 (128 download)
Download or read book Low-order Modeling of Unsteady Aerodynamic Forces written by Xuanhong An and published by . This book was released on 2018 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Juan Carlos Gomez
Publisher :
ISBN 13 :
Total Pages : 96 pages
Book Rating : 4.:/5 (932 download)
Download or read book Low-Order Modeling of the Unsteady Aerodynamics in Flapping Wings written by Juan Carlos Gomez and published by . This book was released on 2015 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: The investigation of unsteady aerodynamics is becoming a more attractive topic of research in enhancing flight capabilities. Natural flyers such as birds and insects can undergo flight maneuvers that are very difficult or not possible with current aerodynamic understanding. Modeling the unsteady phenomena produced by flapping wings is important to the understanding of these maneuvers, with possible applications to aircraft flight. We investigate reduced-order modeling of the unsteady aerodynamics generated by flapping wings using the two separate approaches of rotational lift and dynamic stall. A low order quasi steady model based on rotational lift and a revised version incorporating dynamic stall are presented. Both concepts are analyzed using simulated results, with experimental data measured with matching kinematics as a basis of comparison. This combined model is then used to conduct parametric studies of the time averaged aerodynamic forces over varying kinematic variables.
Author : National Aeronautics and Space Administration (NASA)
Publisher : Createspace Independent Publishing Platform
ISBN 13 : 9781722379582
Total Pages : 28 pages
Book Rating : 4.3/5 (795 download)
Download or read book Modeling of Aircraft Unsteady Aerodynamic Characteristics. Part 1 written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-05 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: A short theoretical study of aircraft aerodynamic model equations with unsteady effects is presented. The aerodynamic forces and moments are expressed in terms of indicial functions or internal state variables. The first representation leads to aircraft integro-differential equations of motion; the second preserves the state-space form of the model equations. The formulations of unsteady aerodynamics is applied in two examples. The first example deals with a one-degree-of-freedom harmonic motion about one of the aircraft body axes. In the second example, the equations for longitudinal short-period motion are developed. In these examples, only linear aerodynamic terms are considered. The indicial functions are postulated as simple exponentials and the internal state variables are governed by linear, time-invariant, first-order differential equations. It is shown that both approaches to the modeling of unsteady aerodynamics lead to identical models. Klein, Vladislav and Noderer, Keith D. Langley Research Center RTOP 505-64-52-01...
Author :
Publisher :
ISBN 13 :
Total Pages : 30 pages
Book Rating : 4.:/5 (317 download)
Download or read book Modeling of Aircraft Unsteady Aerodynamic Characteristics. Part 1: Postulated Models written by and published by . This book was released on 1994 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Arturo Villegas Vaquero
Publisher :
ISBN 13 :
Total Pages : 150 pages
Book Rating : 4.:/5 (889 download)
Download or read book Evaluation of Unsteady Aerodynamic Forces and Pressure in Wings and Turbines at Low Reynolds Number by Combining Particle Image Velocimetry and Proper Orthogonal Decomposition written by Arturo Villegas Vaquero and published by . This book was released on 2014 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aerodynamic unsteady forces in stationary and rotating wings are analyzed in this dissertation by using a combination of time-resolved particle image velocimetry (TR-PIV) and proper orthogonal decomposition (POD) techniques. Recent progress in experimental measurements has demonstrated the use of TR-PIV to calculate forces by applying the integral conservation of momentum equation in its different forms. However, a more accurate and robust method is needed for unsteady forces calculations. With this in mind, a modified pressure Poisson method is developed and applied in this work, showing its superior behavior compared to other methodologies described in the past. The independence of the calculated forces shows the robustness and stability of the method. Whereas force calculations have been recently considered, the role of flow structures in force fluctuations has not been revealed yet and it is the main focus of this study. To elucidate these relations, a hybrid PIV-POD analysis is applied to reconstruct the velocity field from the most energetic modes of the flow. A model describing the vortex-force relations is proposed in terms of lift and drag variations during the vortex shedding process. A spectral analysis of the calculated forces suggests symmetric periodic lift, drag and circulation variations at the shedding frequency. Moreover, lift, drag and circulation signals are in phase, which supports lift-circulation proportionality. However, non-symmetric drag fluctuations are found at double the shedding frequency within a shedding cycle. For instance, when a positive or negative circulation vortex detaches, different values in the maximum and minimum drag are obtained. The data and physical relations obtained in this work such as main frequencies, vortex-force fluctuations and behavior of reduced-order models can aid in the development of CFD applications at low Rey . The methodology described can be applied to any moving or stationary wing at different Reynolds numbers and angles of attack which would provide additional data for numerical codes. Furthermore, accurate measurements of unsteady forces allow determining narrower and more precise safety margins. Moreover, these measurements could be of application in flow control since forces are related to flow features simultaneously.
Author : Jeffrey P. Thomas
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (11 download)
Download or read book A Static/dynamic Correction Approach for Reduced-order Modeling of Unsteady Aerodynamics written by Jeffrey P. Thomas and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : E.H. Dowell
Publisher : Springer Science & Business Media
ISBN 13 : 9401104999
Total Pages : 724 pages
Book Rating : 4.4/5 (11 download)
Download or read book A Modern Course in Aeroelasticity written by E.H. Dowell and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 724 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aeroelasticity is the study of flexible structures situated in a flowing fluid. Its modern origins are in the field of aerospace engineering, but it has now expanded to include phenomena arising in other fields such as bioengineering, civil engineering, mechanical engineering and nuclear engineering. The present volume is a teaching text for a first, and possibly second, course in aeroelasticity. It will also be useful as a reference source on the fundamentals of the subject for practitioners. In this third edition, several chapters have been revised and three new chapters added. The latter include a brief introduction to `Experimental Aeroelasticity', an overview of a frontier of research `Nonlinear Aeroelasticity', and the first connected, authoritative account of `Aeroelastic Control' in book form. The authors are drawn from a range of fields including aerospace engineering, civil engineering, mechanical engineering, rotorcraft and turbomachinery. Each author is a leading expert in the subject of his chapter and has many years of experience in consulting, research and teaching.
Author : H. J. Dunn
Publisher :
ISBN 13 :
Total Pages : 36 pages
Book Rating : 4.:/5 (31 download)
Download or read book An Analytical Technique for Approximating Unsteady Aerodynamics in the Time Domain written by H. J. Dunn and published by . This book was released on 1980 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : David Nixon
Publisher :
ISBN 13 :
Total Pages : 410 pages
Book Rating : 4.3/5 (91 download)
Download or read book Unsteady Transonic Aerodynamics written by David Nixon and published by . This book was released on 1989 with total page 410 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume complements Transonic aerodynamics (v.81 in the series) which is concerned with steady flow. This is the only book to address the subject of unsteady transonic aerodynamics, a field much different from steady aerodynamics. The most pronounced difference is the complex shock wave motions
Author : H.M. Atassi
Publisher : Springer Science & Business Media
ISBN 13 : 1461393418
Total Pages : 876 pages
Book Rating : 4.4/5 (613 download)
Download or read book Unsteady Aerodynamics, Aeroacoustics, and Aeroelasticity of Turbomachines and Propellers written by H.M. Atassi and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 876 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first International Symposium on Unsteady Aerodynamics and Aero elasticity of Turbomachines was held in Paris in 1976, and was followed by symposia at Lausanne in 1980, Cambridge in 1984, Aachen in 1987, Bei jing in 1989, and Notre Dame in 1991. The proceedings published following these symposia have become recognized both as basic reference texts in the subject area and as useful guides to progress in the field. It is hoped that this volume, which represents the proceedings of the Sixth International Symposium on Unsteady Aerodynamics of Turbomachines, will continue that tradition. Interest in the unsteady aerodynamics, aeroacoustics, and aeroelasticity of turbomachines has been growing rapidly since the Paris symposium. This expanded interest is reflected by a significant increase in the numbers of contributed papers and symposium participants. The timeliness of the topics has always been an essential objective of these symposia. Another important objective is to promote an international exchange between scien tists and engineers from universities, government agencies, and industry on the fascinating phenomena of unsteady turbomachine flows and how they affect the aeroelastic stability of the blading system and cause the radiation of unwanted noise. This exchange acts as a catalyst for the development of new analytical and numerical models along with carefully designed ex periments to help understand the behavior of such systems and to develop predictive tools for engineering applications.
Author : P.G. Tucker
Publisher : Springer Science & Business Media
ISBN 13 : 9400770499
Total Pages : 432 pages
Book Rating : 4.4/5 (7 download)
Download or read book Unsteady Computational Fluid Dynamics in Aeronautics written by P.G. Tucker and published by Springer Science & Business Media. This book was released on 2013-08-30 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt: The field of Large Eddy Simulation (LES) and hybrids is a vibrant research area. This book runs through all the potential unsteady modelling fidelity ranges, from low-order to LES. The latter is probably the highest fidelity for practical aerospace systems modelling. Cutting edge new frontiers are defined. One example of a pressing environmental concern is noise. For the accurate prediction of this, unsteady modelling is needed. Hence computational aeroacoustics is explored. It is also emerging that there is a critical need for coupled simulations. Hence, this area is also considered and the tensions of utilizing such simulations with the already expensive LES. This work has relevance to the general field of CFD and LES and to a wide variety of non-aerospace aerodynamic systems (e.g. cars, submarines, ships, electronics, buildings). Topics treated include unsteady flow techniques; LES and hybrids; general numerical methods; computational aeroacoustics; computational aeroelasticity; coupled simulations and turbulence and its modelling (LES, RANS, transition, VLES, URANS). The volume concludes by pointing forward to future horizons and in particular the industrial use of LES. The writing style is accessible and useful to both academics and industrial practitioners. From the reviews: "Tucker's volume provides a very welcome, concise discussion of current capabilities for simulating and modellng unsteady aerodynamic flows. It covers the various pos sible numerical techniques in good, clear detail and presents a very wide range of practical applications; beautifully illustrated in many cases. This book thus provides a valuable text for practicing engineers, a rich source of background information for students and those new to this area of Research & Development, and an excellent state-of-the-art review for others. A great achievement." Mark Savill FHEA, FRAeS, C.Eng, Professor of Computational Aerodynamics Design & Head of Power & Propulsion Sciences, Department of Power & Propulsion, School of Engineering, Cranfield University, Bedfordshire, U.K. "This is a very useful book with a wide coverage of many aspects in unsteady aerodynamics method development and applications for internal and external flows." L. He, Rolls-Royce/RAEng Chair of Computational Aerothermal Engineering, Oxford University, U.K. "This comprehensive book ranges from classical concepts in both numerical methods and turbulence modelling approaches for the beginner to latest state-of-the-art for the advanced practitioner and constitutes an extremely valuable contribution to the specific Computational Fluid Dynamics literature in Aeronautics. Student and expert alike will benefit greatly by reading it from cover to cover." Sébastien Deck, Onera, Meudon, France
Author :
Publisher :
ISBN 13 :
Total Pages : 16 pages
Book Rating : 4.:/5 (317 download)
Download or read book Aeroservoelastic Modeling and Applications Using Minimum-state Approximations of the Unsteady Aerodynamics written by and published by . This book was released on 1989 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Diederik Beckers
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (139 download)
Download or read book Fast Models and Reinforcement Learning Control of Unsteady Aerodynamics written by Diederik Beckers and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Large amplitude flow disturbances and gusts can drastically alter the aerodynamic forces on airfoils or structures. The modeling and control of the aerodynamic response of the flow around the body is complicated by the inherent nonlinearities and high dimensionality of this system, which increase the cost and complexity of the numerical tools that enable this. This work introduces two numerical tools for the efficient modeling of unsteady aerodynamic flows and explores the use of deep reinforcement learning to perform airfoil pitch control during flow disturbances. The first numerical tool we introduce is a grid-based potential flow solver. We focus on the discrete streamfunction and model the flow around bodies and point vortices immersed in a cartesian grid. This tool reformulates the inviscid vortex-in-cell method as a saddle-point problem where constraints such as the no-flow-through and Kutta condition can be added as Lagrange multipliers. The second numerical tool uses a potential flow to model wind tunnel walls and irrotational wind tunnel gust generators in a viscous flow simulation. This technique allows us to still accurately model the flow around the test subject while accounting for the effects of the wind tunnel in a way that doesn't drastically increase the cost of the simulation. Lastly, in our explorative study of reinforcement learning of airfoil pitch control, we try out the training of a control policy in a classical unsteady aerodynamics environment and a viscous, low-Reynolds number flow environment to minimize the lift variations caused by flow disturbances and compare the performance of controllers, or agents, that observe different types of information about the states of the system.
Author : Omar Darío López Mejia
Publisher : Springer
ISBN 13 : 331962136X
Total Pages : 118 pages
Book Rating : 4.3/5 (196 download)
Download or read book Numerical Simulation of the Aerodynamics of High-Lift Configurations written by Omar Darío López Mejia and published by Springer. This book was released on 2018-04-10 with total page 118 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book deals with numerical simulations and computations of the turbulent flow around high-lift configurations commonly used in aircraft. It is devoted to the Computational Fluids Dynamics (CFD) method using full Navier-Stokes solvers typically used in the simulation of high-lift configuration. With the increase of computational resources in the aeronautical industry, the computation of complex flows such as the aerodynamics of high-lift configurations has become an active field not only in academic but also in industrial environments. The scope of the book includes applications and topics of interest related to the simulation of high-lift configurations such as: lift and drag prediction, unsteady aerodynamics, low Reynolds effects, high performance computing, turbulence modelling, flow feature visualization, among others. This book gives a description of the state-of-the-art of computational models for simulation of high-lift configurations. It also shows and discusses numerical results and validation of these computational models. Finally, this book is a good reference for graduate students and researchers interested in the field of simulation of high-lift configurations.
Author : National Aeronautics and Space Adm Nasa
Publisher :
ISBN 13 : 9781728993126
Total Pages : 30 pages
Book Rating : 4.9/5 (931 download)
Download or read book Semi-Empirical Model for Prediction of Unsteady Forces on an Airfoil with Application to Flutter written by National Aeronautics and Space Adm Nasa and published by . This book was released on 2018-10-19 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: A semi-empirical model is described for predicting unsteady aerodynamic forces on arbitrary airfoils under mildly stalled and unstalled conditions. Aerodynamic forces are modeled using second order ordinary differential equations for lift and moment with airfoil motion as the input. This model is simultaneously integrated with structural dynamics equations to determine flutter characteristics for a two degrees-of-freedom system. Results for a number of cases are presented to demonstrate the suitability of this model to predict flutter. Comparison is made to the flutter characteristics determined by a Navier-Stokes solver and also the classical incompressible potential flow theory. Mahajan, Aparajit J. and Kaza, Krishna Rao V. Glenn Research Center RTOP 535-03-10...
Author : Velimir Jurdjevic
Publisher : Cambridge University Press
ISBN 13 : 0521495024
Total Pages : 516 pages
Book Rating : 4.5/5 (214 download)
Download or read book Geometric Control Theory written by Velimir Jurdjevic and published by Cambridge University Press. This book was released on 1997 with total page 516 pages. Available in PDF, EPUB and Kindle. Book excerpt: Geometric control theory is concerned with the evolution of systems subject to physical laws but having some degree of freedom through which motion is to be controlled. This book describes the mathematical theory inspired by the irreversible nature of time evolving events. The first part of the book deals with the issue of being able to steer the system from any point of departure to any desired destination. The second part deals with optimal control, the question of finding the best possible course. An overlap with mathematical physics is demonstrated by the Maximum principle, a fundamental principle of optimality arising from geometric control, which is applied to time-evolving systems governed by physics as well as to man-made systems governed by controls. Applications are drawn from geometry, mechanics, and control of dynamical systems. The geometric language in which the results are expressed allows clear visual interpretations and makes the book accessible to physicists and engineers as well as to mathematicians.
Author : L. V. Andrew
Publisher :
ISBN 13 :
Total Pages : 82 pages
Book Rating : 4.3/5 (91 download)
Download or read book Unsteady Aerodynamic Pressures in Transonic Flow written by L. V. Andrew and published by . This book was released on 1971 with total page 82 pages. Available in PDF, EPUB and Kindle. Book excerpt: Oscillatory pressures as well as total loads were obtained on a 70-degree delta-wing model undergoing sinusoidal pitch rotation in transonic flow. The mach number range was from 0.8 to 1.2, and the maximum reduced frequency (based on centerline half chord) achieved was 0.172. Corresponding pressures were computer using the kernel function method and the doublet/vortex lattice method at subsonic speeds, the sonic box method, and the supersonic mach box method. Both box methods produce point values of potentials that are fitted by surfaces tyo yeld pressures. Comparisomns of the measured and computer pressures show that, in general (and as expected), the computed pressures are higher than the measured values near the leading edge. Also, in general (but unexpected), the computed phase lags between motion of the surface and the pressures generated by the motion are lower than the measure values.
