An Analytical Technique For Approximating Unsteady Aerodynamics In The Time Domain PDF Download
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Author | : National Aeronautics and Space Administration (NASA) |
Publisher | : Createspace Independent Publishing Platform |
Total Pages | : 32 |
Release | : 2018-08-14 |
Genre | : |
ISBN | : 9781725553798 |
Download An Analytical Technique for Approximating Unsteady Aerodynamics in the Time Domain Book in PDF, ePub and Kindle
An analytical technique is presented for approximating unsteady aerodynamic forces in the time domain. The order of elements of a matrix Pade approximation was postulated, and the resulting polynomial coefficients were determined through a combination of least squares estimates for the numerator coefficients and a constrained gradient search for the denominator coefficients which insures stable approximating functions. The number of differential equations required to represent the aerodynamic forces to a given accuracy tends to be smaller than that employed in certain existing techniques where the denominator coefficients are chosen a priori. Results are shown for an aeroelastic, cantilevered, semispan wing which indicate a good fit to the aerodynamic forces for oscillatory motion can be achieved with a matrix Pade approximation having fourth order numerator and second order denominator polynomials. Dunn, H. J. Langley Research Center NASA-TP-1738, L-13255 RTOP 505-34-33-02...
Author | : H. J. Dunn |
Publisher | : |
Total Pages | : 36 |
Release | : 1980 |
Genre | : |
ISBN | : |
Download An Analytical Technique for Approximating Unsteady Aerodynamics in the Time Domain Book in PDF, ePub and Kindle
Author | : H. J. Dunn |
Publisher | : |
Total Pages | : 36 |
Release | : 1980 |
Genre | : Aeroelasticity |
ISBN | : |
Download An Analytical Technique for Approximating Unsteady Aerodynamics in the Time Domain Book in PDF, ePub and Kindle
Author | : |
Publisher | : |
Total Pages | : 52 |
Release | : 1991 |
Genre | : Science |
ISBN | : |
Download NASA Technical Paper Book in PDF, ePub and Kindle
Author | : National Aeronautics and Space Adm Nasa |
Publisher | : Independently Published |
Total Pages | : 52 |
Release | : 2018-10-25 |
Genre | : Science |
ISBN | : 9781729230886 |
Download Physically Weighted Approximations of Unsteady Aerodynamic Forces Using the Minimum-State Method Book in PDF, ePub and Kindle
The Minimum-State Method for rational approximation of unsteady aerodynamic force coefficient matrices, modified to allow physical weighting of the tabulated aerodynamic data, is presented. The approximation formula and the associated time-domain, state-space, open-loop equations of motion are given, and the numerical procedure for calculating the approximation matrices, with weighted data and with various equality constraints are described. Two data weighting options are presented. The first weighting is for normalizing the aerodynamic data to maximum unit value of each aerodynamic coefficient. The second weighting is one in which each tabulated coefficient, at each reduced frequency value, is weighted according to the effect of an incremental error of this coefficient on aeroelastic characteristics of the system. This weighting yields a better fit of the more important terms, at the expense of less important ones. The resulting approximate yields a relatively low number of aerodynamic lag states in the subsequent state-space model. The formulation forms the basis of the MIST computer program which is written in FORTRAN for use on the MicroVAX computer and interfaces with NASA's Interaction of Structures, Aerodynamics and Controls (ISAC) computer program. The program structure, capabilities and interfaces are outlined in the appendices, and a numerical example which utilizes Rockwell's Active Flexible Wing (AFW) model is given and discussed. Karpel, Mordechay and Hoadley, Sherwood Tiffany Langley Research Center RTOP 505-63-21-04
Author | : Nasa Technical Reports Server (Ntrs) |
Publisher | : BiblioGov |
Total Pages | : 28 |
Release | : 2013-07 |
Genre | : |
ISBN | : 9781289195885 |
Download Application of Approximate Unsteady Aerodynamics for Flutter Analysis Book in PDF, ePub and Kindle
A technique for approximating the modal aerodynamic influence coefficient (AIC) matrices by using basis functions has been developed. A process for using the resulting approximated modal AIC matrix in aeroelastic analysis has also been developed. The method requires the unsteady aerodynamics in frequency domain, and this methodology can be applied to the unsteady subsonic, transonic, and supersonic aerodynamics. The flutter solution can be found by the classic methods, such as rational function approximation, k, p-k, p, root locus et cetera. The unsteady aeroelastic analysis using unsteady subsonic aerodynamic approximation is demonstrated herein. The technique presented is shown to offer consistent flutter speed prediction on an aerostructures test wing (ATW) 2 and a hybrid wing body (HWB) type of vehicle configuration with negligible loss in precision. This method computes AICs that are functions of the changing parameters being studied and are generated within minutes of CPU time instead of hours. These results may have practical application in parametric flutter analyses as well as more efficient multidisciplinary design and optimization studies.
Author | : David Eller |
Publisher | : |
Total Pages | : 33 |
Release | : 2003 |
Genre | : |
ISBN | : |
Download On an Efficient Method for Time-domain Unsteady Aerodynamics Book in PDF, ePub and Kindle
Author | : Grigorios Dimitriadis |
Publisher | : John Wiley & Sons |
Total Pages | : 597 |
Release | : 2017-05-01 |
Genre | : Technology & Engineering |
ISBN | : 1118613473 |
Download Introduction to Nonlinear Aeroelasticity Book in PDF, ePub and Kindle
Introduces the latest developments and technologies in the area of nonlinear aeroelasticity Nonlinear aeroelasticity has become an increasingly popular research area in recent years. There have been many driving forces behind this development, increasingly flexible structures, nonlinear control laws, materials with nonlinear characteristics, etc. Introduction to Nonlinear Aeroelasticity covers the theoretical basics in nonlinear aeroelasticity and applies the theory to practical problems. As nonlinear aeroelasticity is a combined topic, necessitating expertise from different areas, the book introduces methodologies from a variety of disciplines such as nonlinear dynamics, bifurcation analysis, unsteady aerodynamics, non-smooth systems and others. The emphasis throughout is on the practical application of the theories and methods, so as to enable the reader to apply their newly acquired knowledge. Key features: Covers the major topics in nonlinear aeroelasticity, from the galloping of cables to supersonic panel flutter. Discusses nonlinear dynamics, bifurcation analysis, numerical continuation, unsteady aerodynamics and non-smooth systems. Considers the practical application of the theories and methods. Covers nonlinear dynamics, bifurcation analysis and numerical methods. Accompanied by a website hosting Matlab code. Introduction to Nonlinear Aeroelasticity is a comprehensive reference for researchers and workers in industry and is also a useful introduction to the subject for graduate and undergraduate students across engineering disciplines.
Author | : |
Publisher | : |
Total Pages | : 892 |
Release | : 1994 |
Genre | : Aeronautics |
ISBN | : |
Download Scientific and Technical Aerospace Reports Book in PDF, ePub and Kindle
Author | : E. H. Dowell |
Publisher | : |
Total Pages | : 46 |
Release | : 1980 |
Genre | : Aerodynamics |
ISBN | : |
Download A Simple Method for Converting Frequency-domain Aerodynamics to the Time Domain Book in PDF, ePub and Kindle