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Limit Cycle Oscillations Lco And Nonlinear Aeroelastic Wing Response
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Book Synopsis Limit Cycle Oscillations (LCO) and Nonlinear Aeroelastic Wing Response by : Earl H. Dowell
Download or read book Limit Cycle Oscillations (LCO) and Nonlinear Aeroelastic Wing Response written by Earl H. Dowell and published by . This book was released on 1996 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: Limit cycle oscillations (LCO) have been observed for elastic wings at moderate to high angles of attack where separated flow is thought to occur. At transonic flow conditions with shock waves present, flow separation may occur at moderate angles of attack. For higher angles of attack, separation may occur at (low) subsonic conditions. Empirical quasi steady aerodynamic models based on steady state experimental data have shown some success in predicting the observed LCO. New theoretical aeroelastic models are proposed here to improve the prediction of LCO. Also proposed are simple, flow speed experiments to validate these theoretical models with an option for high speed experiments as well.
Book Synopsis Limit Cycle Oscillations (LCO) and Nonlinear Aeroelastic Wing Response by :
Download or read book Limit Cycle Oscillations (LCO) and Nonlinear Aeroelastic Wing Response written by and published by . This book was released on 1996 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Limit cycle oscillations (LCO) have been observed for elastic wings at moderate to high angles of attack where separated flow is thought to occur. At transonic flow conditions with shock waves present, flow separation may occur at moderate angles of attack. For higher angles of attack, separation may occur at (low) subsonic conditions. Empirical quasi steady aerodynamic models based on steady state experimental data have shown some success in predicting the observed LCO. New theoretical aeroelastic models are proposed here to improve the prediction of LCO. Also proposed are simple, flow speed experiments to validate these theoretical models with an option for high speed experiments as well.
Book Synopsis Limit Cycle Oscillations (LCO) and Nonlinear Aeroelastic Wing Response: Reduced Order Aerodynamic Models by : Earl Dowell
Download or read book Limit Cycle Oscillations (LCO) and Nonlinear Aeroelastic Wing Response: Reduced Order Aerodynamic Models written by Earl Dowell and published by . This book was released on 1999 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: A nonlinear, aeroelastic analysis of a low aspect, delta wing modeled as a plate of constant thickness demonstrates that limit cycle oscillations (LCO) of the order of the plate thickness are possible. The structural nonlinearity arises from double bending in both the chordwise and spanwise directions. The present results using a vortex lattice aerodynamic model for a low Mach number flow complement earlier studies for rectangular wing platforms that showed similar qualitative results. The theoretical results for the flutter boundary (beyond which LCO occurs) have been validated by comparison to the experimental data reported by other investigators for the low aspect ratio delta wings. Also the limit cycle oscillations found experimentally by previous investigators (but not previously quantified prior to the present work) are consistent with the theoretical results reported here. Reduced order aerodynamic and structural models are used to substantially decrease computational cost with no loss in accuracy. Without the use of reduced order models, calculations of the LCO would be impractical. A wind tunnel model is tested to provide a quantitative experimental correlation with the theoretical results for the LCO response itself.
Book Synopsis Limit Cycle Oscillations and Nonlinear Aeroelastic Wing Response: Reduced Order Aerodynamic Models by :
Download or read book Limit Cycle Oscillations and Nonlinear Aeroelastic Wing Response: Reduced Order Aerodynamic Models written by and published by . This book was released on 2003 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: To develop an eigenmode or proper orthogonal decomposition (POD) modal representation of unsteady aerodynamic forces on oscillating flexible airfoils and wings and thereby reduce the size and cost of mathematical models for such forces by several orders of magnitude. Building on earlier work for two-dimensional inviscid flows, we seek to extend our models to. three-dimensional flows with viscous effects included. Also a novel form of the harmonic balance (HB) method had been developed for determining limit cycle oscillations (LCO) of aeroelastic systems.
Book Synopsis Limit Cycle Oscillations and Nonlinear Aeroelastic Wing Response: Reduced Order Aerodynamic Models by :
Download or read book Limit Cycle Oscillations and Nonlinear Aeroelastic Wing Response: Reduced Order Aerodynamic Models written by and published by . This book was released on 2003 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: To develop an eigenmode or proper orthogonal decomposition (POD) modal representation of unsteady aerodynamic forces on oscillating flexible airfoils and wings and thereby reduce the size and cost of mathematical models for such forces by several orders of magnitude. Building on earlier work for two-dimensional inviscid flows, we seek to extend our models to. three-dimensional flows with viscous effects included. Also a novel form of the harmonic balance (HB) method had been developed for determining limit cycle oscillations (LCO) of aeroelastic systems.
Book Synopsis Limit Cycle Oscillations and Nonlinear Aeroelastic Wing Response by : Earl H. Dowell
Download or read book Limit Cycle Oscillations and Nonlinear Aeroelastic Wing Response written by Earl H. Dowell and published by . This book was released on 2004 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Theoretical and Experimental Investigations of Internal Resonances, and Related Behavior, in Nonlinear Aeroelastic Systems by : Thomas W. Strganac
Download or read book Theoretical and Experimental Investigations of Internal Resonances, and Related Behavior, in Nonlinear Aeroelastic Systems written by Thomas W. Strganac and published by . This book was released on 2004 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Generic Nonlinear Aeroelastic Method with Semi-empirical Nonlinear Unsteady Aerodynamics by : Atlee M. Cunningham
Download or read book A Generic Nonlinear Aeroelastic Method with Semi-empirical Nonlinear Unsteady Aerodynamics written by Atlee M. Cunningham and published by . This book was released on 1999 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fluid-structure interactions (FSI) that involve nonlinear aerodynamic forces are described which affect both aging aircraft, as well as new aircraft. Several cases are presented which contain aerodynamic non linearities that are important in the FSI process and that require different solution approaches from those taken for linear FSI problems. A time-dependent approach is presented which is based on a semi empirical nonlinear aerodynamic model that is fully coupled with the aircraft elastic equations of motion. An early version of this methodology is applied to a wide variety of Limit Cycle Oscillation (LCO) cases for a fighter configuration carrying large underwing stores. The new method is applied to three classes of problems: (1) LCO for bomber and transport type configurations; (2) LCO for a fighter wing; and (3) large amplitude buffet response of a fin subject to server wake turbulence.
Book Synopsis A Generic Nonlinear Aeroelastic Method with Semi-empirical Nonlinear Unsteady Aerodynamics by : Atlee M. Cunningham
Download or read book A Generic Nonlinear Aeroelastic Method with Semi-empirical Nonlinear Unsteady Aerodynamics written by Atlee M. Cunningham and published by . This book was released on 1999 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fluid-structure interactions (FSI) that involve nonlinear aerodynamic forces are described which affect both aging aircraft, as well as new aircraft. Several cases are presented which contain aerodynamic non linearities that are important in the FSI process and that require different solution approaches from those taken for linear FSI problems. A time-dependent approach is presented which is based on a semi empirical nonlinear aerodynamic model that is fully coupled with the aircraft elastic equations of motion. An early version of this methodology is applied to a wide variety of Limit Cycle Oscillation (LCO) cases for a fighter configuration carrying large underwing stores. The new method is applied to three classes of problems: (1) LCO for bomber and transport type configurations; (2) LCO for a fighter wing; and (3) large amplitude buffet response of a fin subject to server wake turbulence.
Book Synopsis A Study of Uncertainties in Nonlinear Aeroelastic Systems by : Earl H. Dowell
Download or read book A Study of Uncertainties in Nonlinear Aeroelastic Systems written by Earl H. Dowell and published by . This book was released on 2007 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: A principal goal of the Air Force research program is to develop accurate, reliable and efficient computational models so that laboratory and flight tests may be decreased and/or the results of such tests may be more effective in reducing design and production costs of new Air Force systems. Key challenges in achieving this goal are the uncertainties that exist in computational models. These uncertainties may be a result of the limitations of the mathematical model in representing physical reality, the numerical uncertainties that arise in obtaining (computational) solitions to these models, and/or the uncertainties in the parameters that enter into such models. Examples of each of these uncertainties have been studied for nonlinear aeroelastic systems and the computational results compared with experiment. New highly computationally efficient methods have been developed.
Book Synopsis Variability and Model Adequacy in Simulations of Store-induced Limit Cycle Oscillations by : Ashley Scott Myers
Download or read book Variability and Model Adequacy in Simulations of Store-induced Limit Cycle Oscillations written by Ashley Scott Myers and published by . This book was released on 2007 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt: A prominent phenomenon of the transonic flight regime is the potential for limit cycle oscillation (LCO) development. LCO is a stable oscillation produced by aeroelastic interactions within a component of the aircraft. Such oscillation shortens the fatigue life of the aircraft and increases the amount of maintenance necessary. These aspects are of great concern to the aerospace industry, particularly with high performance military aircraft that are required to operate beyond their planned service lives. The research here focused specifically on the aircraft wing and the influence of external stores attached to that wing on its aeroelastic properties. Monte Carlo simulations were performed to estimate the probability of a wing undergoing limit cycle oscillations due to external stores. Simulations were conducted with a finite element structural model of a wing coupled with multiple subsonic and transonic unsteady aerodynamics solvers to compare computational cost and accuracy. The results provide guidance for implementing probabilistic analysis methods with industry-standard software to predict dangerous aeroelastic response processes that sometimes occur during flight tests. For the low transitional Mach numbers (between 0.7 and 0.88), the linear aerodynamic model was found to be a viable alternative to the more computationally costly alternatives. For Mach numbers above 0.88, nonlinear, viscous methods were necessary.
Book Synopsis A Modern Course in Aeroelasticity by : Earl H. Dowell
Download or read book A Modern Course in Aeroelasticity written by Earl H. Dowell and published by Springer Nature. This book was released on 2021-10-16 with total page 828 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is the sixth edition. It is suitable for one or more courses at the advanced undergraduate level and graduate level to cover the field of aeroelasticity. It is also of value to the research scholar and engineering practitioner who wish to understand the state of the art in the field. This book covers the basics of aeroelasticity or the dynamics of fluid–structure interaction. While the field began in response to the rapid development of aviation, it has now expanded into many branches of engineering and scientific disciplines and treats physical phenomena from aerospace engineering, bioengineering, civil engineering, and mechanical engineering in addition to drawing the attention of mathematicians and physicists. The basic questions addressed are dynamic stability and response of fluid structural systems as revealed by both linear and nonlinear mathematical models and correlation with experiment. The use of scaled models and full-scale experiments and tests play a key role where theory is not considered sufficiently reliable.
Book Synopsis Impact of Structural Damping Nonlinearity in Transonic Limit Cycle Oscillations (LCO). by :
Download or read book Impact of Structural Damping Nonlinearity in Transonic Limit Cycle Oscillations (LCO). written by and published by . This book was released on 2005 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: The focus of this research has been on the assessment of the effects of internal friction on the response of aeroelastic systems exhibiting either explosive flutter or limit cycle oscillations to provide a confirmation of the potential of friction as a significant stabilizing factor in the limit cycle oscillations observed on several aircraft, e.g. F- 16. The work performed in this regard can broadly be divided into three major efforts, two computational/ theoretical and one experimental: (1) the analysis of the effects of friction on a structural dynamic systems in which the effects of the aerodynamic forces have been modeled. The computational expediency of this simple model allowed to analyze and study a vast array of cases from which broad conclusions were derived the validity of which was later extended to the complex models of task (2). (2) the analysis of the effects of friction on actual aeroelastic systems, i.e. airfoil and flat plate in a uniform flow, in which the aerodynamic forces are computed in time in parallel to the structural dynamic analysis in a tight coupling format. (3) the experimental testing in the DLR- Gottingen (Germany) Transonic wind tunnel of a NLR7301 airfoil equipped with a friction device similar to the ones studied in tasks (1) and (2). This effort was followed by a data analysis that revealed mostly similarities, albeit a few differences, with the theoretical results of tasks (1) and (2) above.
Book Synopsis Nonlinear Oscillations by : Ali H. Nayfeh
Download or read book Nonlinear Oscillations written by Ali H. Nayfeh and published by John Wiley & Sons. This book was released on 2008-09-26 with total page 720 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nonlinear Oscillations is a self-contained and thorough treatment of the vigorous research that has occurred in nonlinear mechanics since 1970. The book begins with fundamental concepts and techniques of analysis and progresses through recent developments and provides an overview that abstracts and introduces main nonlinear phenomena. It treats systems having a single degree of freedom, introducing basic concepts and analytical methods, and extends concepts and methods to systems having degrees of freedom. Most of this material cannot be found in any other text. Nonlinear Oscillations uses simple physical examples to explain nonlinear dispersive and nondispersive waves. The notation is unified and the analysis modified to conform to discussions. Solutions are worked out in detail for numerous examples, results are plotted and explanations are couched in physical terms. The book contains an extensive bibliography.
Book Synopsis Dynamics and Control of Nonlinear Fluid-structure Interaction by : Robert L. Clark (Jr.)
Download or read book Dynamics and Control of Nonlinear Fluid-structure Interaction written by Robert L. Clark (Jr.) and published by . This book was released on 2003 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Introduction to Aircraft Aeroelasticity and Loads by : Jan Robert Wright
Download or read book Introduction to Aircraft Aeroelasticity and Loads written by Jan Robert Wright and published by John Wiley & Sons. This book was released on 2008-02-08 with total page 527 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aircraft performance is influenced significantly both by aeroelastic phenomena, arising from the interaction of elastic, inertial and aerodynamic forces, and by load variations resulting from flight and ground manoeuvres and gust / turbulence encounters. There is a strong link between aeroelasticity and loads, and these topics have become increasingly integrated in recent years. Introduction to Aircraft Aeroelasticity and Loads introduces the reader to the main principles involved in a wide range of aeroelasticity and loads topics. Divided into three sections, the book begins by reviewing the underlying disciplines of vibrations, aerodynamics, loads and control. It goes on to describe simplified models to illustrate aeroelastic behaviour and aircraft response before introducing more advanced methodologies. Finally, it explains how industrial certification requirements for aeroelasticity and loads may be met and relates these to the earlier theoretical approaches used. Presents fundamentals of structural dynamics, aerodynamics, static and dynamic aeroelasticity, response and load calculations and testing techniques. Covers performance issues related to aeroelasticity such as flutter, control effectiveness, divergence and redistribution of lift. Includes up-to-date experimental methods and analysis. Accompanied by a website with MatLAB and SIMULINK programs that relate to the models used. Introduction to Aircraft Aeroelasticity and Loads enables the reader to understand the aeroelastic and loads principles and procedures employed in a modern aircraft design office. It will appeal to final year undergraduate and masters students as well as engineers who are new to the aerospace industry.
Book Synopsis A Modern Course in Aeroelasticity by : Robert Clark
Download or read book A Modern Course in Aeroelasticity written by Robert Clark and published by Springer Science & Business Media. This book was released on 2006-01-24 with total page 770 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this new edition, the fundamental material on classical linear aeroelasticity has been revised. Also new material has been added describing recent results on the research frontiers dealing with nonlinear aeroelasticity as well as major advances in the modelling of unsteady aerodynamic flows using the methods of computational fluid dynamics and reduced order modeling techniques. New chapters on aeroelasticity in turbomachinery and aeroelasticity and the latter chapters for a more advanced course, a graduate seminar or as a reference source for an entrée to the research literature.
