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Impact Of Structural Damping Nonlinearity In Transonic Limit Cycle Oscillations Lco
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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 IUTAM Symposium Transsonicum IV by : H. Sobieczky
Download or read book IUTAM Symposium Transsonicum IV written by H. Sobieczky and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 406 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Symposium Transsonicum" was founded by Klaus Oswatitsch four decades ago when there was clearly a need for a systematic treatment of flow problems in the higher speed regime in aeronautics. The first conference in 1962 brought together scientists concerned with fundamental problems involving the sonic flow speed regime. Results of the conference provided an understanding of some basic tran sonic phenomena by proposing mathematical methods that allowed for the de velopment of practical calculations. The "Transonic Controversy" (about shock free flows) was still an open issue after this meeting. In 1975 the second symposium was held, by then there was much understanding in how to avoid shocks in a steady plane flow to be designed, but still very little was known in unsteady phenomena due to a lack of elucidating experiments. A third meeting in 1988 reflected the availability oflarger computers which allowed the numerical analysis of flows with shocks to a reasonable accuracy. Because we are trying to keep Oswatitsch's heritage in science alive especially in Gottingen, we were asked by the aerospace research community to organize another symposium. Much had been achieved already in the knowledge, techno logy and applications in transonics, so IUT AM had to be convinced that a fourth meeting would not just be a reunion of old friends reminiscing some scientific past. The scientific committee greatly supported my efforts to invite scientists ac tively working in transonic problems which still pose substantial difficulties to ae rospace and turbomachinery industry.
Book Synopsis The Effects of Nonlinear Damping on Post-flutter Behavior Using Geometrically Nonlinear Reduced Order Modeling by : Pengchao Song
Download or read book The Effects of Nonlinear Damping on Post-flutter Behavior Using Geometrically Nonlinear Reduced Order Modeling written by Pengchao Song and published by . This book was released on 2015 with total page 71 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent studies of the occurrence of post-flutter limit cycle oscillations (LCO) of the F-16 have provided good support to the long-standing hypothesis that this phenomenon involves a nonlinear structural damping. A potential mechanism for the appearance of nonlinearity in the damping are the nonlinear geometric effects that arise when the deformations become large enough to exceed the linear regime. In this light, the focus of this investigation is first on extending nonlinear reduced order modeling (ROM) methods to include viscoelasticity which is introduced here through a linear Kelvin-Voigt model in the undeformed configuration. Proceeding with a Galerkin approach, the ROM governing equations of motion are obtained and are found to be of a generalized van der Pol-Duffing form with parameters depending on the structure and the chosen basis functions. An identification approach of the nonlinear damping parameters is next proposed which is applicable to structures modeled within commercial finite element software. The effects of this nonlinear damping mechanism on the post-flutter response is next analyzed on the Goland wing through time-marching of the aeroelastic equations comprising a rational fraction approximation of the linear aerodynamic forces. It is indeed found that the nonlinearity in the damping can stabilize the unstable aerodynamics and lead to finite amplitude limit cycle oscillations even when the stiffness related nonlinear geometric effects are neglected. The incorporation of these latter effects in the model is found to further decrease the amplitude of LCO even though the dominant bending motions do not seem to stiffen as the level of displacements is increased in static analyses.
Book Synopsis A Study of Damping in Nonlinear Oscillations by : Maurice L. Rasmussen
Download or read book A Study of Damping in Nonlinear Oscillations written by Maurice L. Rasmussen and published by . This book was released on 1966 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Vortex Dominated Flows written by Lu Ting and published by World Scientific. This book was released on 2005 with total page 302 pages. Available in PDF, EPUB and Kindle. Book excerpt: Honoring the contributions of one of the field''s leading experts, Lu Ting, this indispensable volume contains important new results at the cutting edge of research. A wide variety of significant new analytical and numerical results in critical areas are presented, including point vortex dynamics, superconductor vortices, cavity flows, vortex breakdown, shock/vortex interaction, wake flows, magneto-hydrodynamics, rotary wake flows, and hypersonic vortex phenomena. The book will be invaluable for those interested in the state of the art of vortex dominated flows, both from a theoretical and applied perspective. Professor Lu Ting and Joe Keller have worked together for over 40 years. In their first joint work entitled OC Periodic vibrations of systems governed by nonlinear partial differential equationsOCO, perturbation analysis and bifurcation theory were used to determine the frequencies and modes of vibration of various physical systems. The novelty was the application to partial differential equations of methods which, previously, had been used almost exclusively on ordinary differential equations. Professsor Lu Ting is an expert in both fluid dynamics and the use of matched asymptotic expansions. His physical insight into fluid flows has led the way to finding the appropriate mathematical simplications used in the solutions to many difficult flow problems."
Book Synopsis A Collection of Technical Papers by :
Download or read book A Collection of Technical Papers written by and published by . This book was released on 2001 with total page 806 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Nonlinear Targeted Energy Transfer in Mechanical and Structural Systems by : Alexander F. Vakakis
Download or read book Nonlinear Targeted Energy Transfer in Mechanical and Structural Systems written by Alexander F. Vakakis and published by Springer Science & Business Media. This book was released on 2008-12-24 with total page 1030 pages. Available in PDF, EPUB and Kindle. Book excerpt: This monograph evolved over a period of nine years from a series of papers and presentations addressing the subject of passive vibration control of mechanical s- tems subjected to broadband, transient inputs. The unifying theme is Targeted - ergy Transfer – TET, which represents a new and unique approach to the passive control problem, in which a strongly nonlinear, fully passive, local attachment, the Nonlinear Energy Sink – NES, is employed to drastically alter the dynamics of the primary system to which it is attached. The intrinsic capacity of the properly - signed NES to promote rapid localization of externally applied (narrowband) - bration or (broadband) shock energy to itself, where it can be captured and dis- pated, provides a powerful strategy for vibration control and the opens the pos- bility for a wide range of applications of TET, such as, vibration and shock i- lation, passive energy harvesting, aeroelastic instability (?utter) suppression, se- mic mitigation, vortex shedding control, enhanced reliability designs (for ex- ple in power grids) and others. The monograph is intended to provide a thorough explanation of the analytical, computational and experimental methods needed to formulate and study TET in mechanical and structural systems. Several prac- cal engineering applications are examined in detail, and experimental veri?cation and validation of the theoretical predictions are provided as well. The authors also suggest a number of possible future applications where application of TET seems promising. The authors are indebted to a number of sponsoring agencies.
Book Synopsis Summary of Flow Modulation and Fluid-Structure Interaction Findings by : Wolfgang Schröder
Download or read book Summary of Flow Modulation and Fluid-Structure Interaction Findings written by Wolfgang Schröder and published by Springer Science & Business Media. This book was released on 2010-05-16 with total page 434 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Collaborative Research Center SFB 401: Flow Modulation and Fluid-Structure Interaction at Airplane Wings investigates numerically and experimentally fundamental problems of very high capacity aircraft having large elastic wings. This issue summarizes the findings of the 12-year research program at RWTH Aachen University which was funded by the Deutsche Forschungsgemeinschaft (DFG) from 1997 through 2008. The research program covered the following three main topics of large transport aircraft: (i) Model flow, wakes, and vortices of airplanes in high-lift-configuration, (ii) Numerical tools for large scale adaptive flow simulation based on multiscale analysis and a parametric mapping concept for grid generation, and (iii) Validated computational design tools based on direct aeroelastic simulation with reduced structural models.
Book Synopsis International Aerospace Abstracts by :
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1999 with total page 1048 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis AIAA Journal by : American Institute of Aeronautics and Astronautics
Download or read book AIAA Journal written by American Institute of Aeronautics and Astronautics and published by . This book was released on 2005 with total page 960 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Nonlinear Transonic Flutter Prediction for F-16 Stores Configuration Clearance by : Raymond G. Toth
Download or read book Nonlinear Transonic Flutter Prediction for F-16 Stores Configuration Clearance written by Raymond G. Toth and published by . This book was released on 2003-03-01 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: Limit cycle oscillation (LCO) has been an issue for the F-16 since its operational deployment. Configuration validation requires large investments in time and resources due to the very specific and stringent guidelines used during flight test to ensure the aircraft does not encounter classical flutter or excessive LCO. A new approach, incorporating inherent nonlinearities that drive LCO is investigated using the Transonic Equivalent Strip method to account for wing thickness effects and shock structure. The g-method flutter solution is used to include first-order aerodynamic damping effects. Two F-16 store configurations are examined to correlate predicted flutter onset speeds, frequencies, and character with those found in flight test, as well as the aerodynamic effect of modeling underwing stores on the flutter solution. Results show small changes in the tuning of the structural model resulted in large changes in the flutter boundary. The aerodynamic influence of underwing stores proved significant, particularly for the two most outboard wing stations. Most importantly, the character of the instability was predicted by the new method.
Book Synopsis MAVRIC Flutter Model Transonic Limit Cycle Oscillation Test by :
Download or read book MAVRIC Flutter Model Transonic Limit Cycle Oscillation Test written by and published by . This book was released on 2001 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Biophysics of Insect Flight by : N. Chari
Download or read book Biophysics of Insect Flight written by N. Chari and published by Springer Nature. This book was released on 2022-01-04 with total page 215 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book basically involves the study of flight parameters, wing beat frequency, moment of inertia, and wing movements for developing various aerodynamic forces which have been calculated. The book is intended for biologists, physicists, nanotechnologists, and aerospace engineers. Resilin, an elastic polymer (4 λ) which is present at the base of insect, plays a major role in Neurogenic and Myogenic insect flyers and influences the physiology of flight muscles. Leading edge vortex (LEV) is a special feature of insect flight. Insect wings have stalling angle above 60 degrees as compared to a man-made aeroplane stalling angle which is 16 degree. Reynolds number, the knowledge of LEV, and detailed study of moment of inertia help in developing flapping flexible wings for micro-aerial-vehicles. This book serves as an interface between biologists and engineers interested to develop biomimicking micro-aerial-vehicles. The contents of this book is useful to researchers and professionals alike.
Book Synopsis Aeroelasticity and Fluid Structure Interaction Problems by : Peretz Friedmann
Download or read book Aeroelasticity and Fluid Structure Interaction Problems written by Peretz Friedmann and published by . This book was released on 1994 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Scientific and Technical Aerospace Reports by :
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 892 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Nonlinear Analysis of Store-induced Limit Cycle Oscillations by : David Eugene Thompson
Download or read book Nonlinear Analysis of Store-induced Limit Cycle Oscillations written by David Eugene Thompson and published by . This book was released on 2001 with total page 422 pages. Available in PDF, EPUB and Kindle. Book excerpt:
