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Explore the interface between aeroelasticity, flight dynamics and control in this fresh, multidisciplinary approach. New insights into the interaction between these fields, rarely separately considered in most modern aircraft, are fully illustrated in this one-of-a-kind book. The comprehensive, systematic coverage will enable the reader to analyse and design next-generation aircraft. Presenting basic concepts in a rigorous yet accessible way, the book builds up to state-of-the-art models through an intuitive step-by-step approach. Both linear and non-linear attributes are covered, and by revisiting classical solutions using modern analysis methods this book provides a unique, modern perspective to bridge the gap between disciplines. Numerous original numerical examples, including online source codes, help to build intuition through hands-on activities. This book will empower the reader to design better and more environmentally friendly aircraft, and is an ideal resource for graduate students, researchers and aerospace engineers.
Trends to lower structural fraction of aircraft increase flexibility effects. Higher bandwidth control systems combined with these more flexible structures cause more aeroservoelastic interactions. Active, closed-loop control systems allow greater flexibility. To take advantage of this design possibility, an integrated ASE model is needed for conceptual and preliminary design stages of aircraft. This report seeks to define the equations of motion of a flexible aircraft from first principles to aid future discussions between experts in the specialties which make up ASE: aerodynamics, controls, and structures. This theoretical report documents the development of the equations, and states under what conditions the assumptions and approximations are accurate. It consists of 5 sections on different technical areas and a summary section: 1) Linearization of flexible aircraft hybrid-coordinate dynamic equations and inclusion of aerodynamic and gravitational loads; 2) Derivation of equations of motion and stability derivatives for a flexible aircraft vehicle; 3) Aerodynamics for aeroservoelasticity; 4) Model-order reduction for linear systems; and 5) Hydraulic actuator equations for aeroservoelastic modeling. Flight control systems; Servomechanisms. (edc).
This book is dedicated to the memory of a distinguished Russian engineer, Rostislav E. Alexeyev, who was the first in the world to develop the largest ground effect machine - Ekranoplan. One of Alexeyev's design concepts with the aerodynamic configuration of a jlying wing can be seen on the front page. The book presents a description of a mathematical model of flow past a lifting system, performing steady and unsteady motions in close proximity to the underlying solid surface (ground). This case is interesting for practical purposes because both the aerodynamic and the economic efficiency of the system near the ground are most pronounced. Use of the method of matched asymptotic expansions enables closed form solutions for the aerodynamic characteristics of the wings-in-ground effect. These can be used for design, identification, and processing of experimental data in the course of developing ground effect vehicles. The term extreme ground effect, widely used through out the book, is associated with very small relative ground clearances of the order of 10% or less. The theory of a lifting surface, moving in immediate proximity to the ground, represents one of the few limiting cases that can be treated analytically. The author would like to acknowledge that this work has been influenced by the ideas of Professor Sheila E. Widnall, who was the first to apply the matched asymptotics techniques to treat lifting flows with the ground effect. Saint Petersburg, Russia February 2000 Kirill V. Rozhdestvensky Contents 1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
pt.3: The dynamic coupling of rigid and elastic degrees of freedom of an airplane are described by two methods. In the first, coupling is described by the changes in airframe characteristic equation roots caused by the introduction of coupling terms to the equations of motion. The second method employs modal response coefficients to compare the relative amplitudes of rigid and elastic degrees of freedom at each coupled mode frequency. Simple literal expressions are obtained for each of these descriptors and physical interpretations given. Time vector diagrams are also used to show the major parameters affecting coupling. (Author).
A constant-angle-of-attack-approach technique was used to measure ground effect on several low -aspect-ratio aircraft. The flight results were compared with results from constant -altitude flybys, wind-tunnel studies, and theoretical prediction data. It was found that the constantangle-of-attack technique provided data that were consistent with data obtained from constant-altitude flybys and required fewer runs to obtain the same amount of data. The test results from an F5D-1 airplane modified with an ogee wing, a prototype F5D-1 airplane, two XB-70 airplanes, and an F-104A airplane indicate that theory and wind-tunnel results adequately predict the trends caused by ground effect as a function of height and aspect ratio. However, the magnitude of these predictions did not always agree with the flightmeasured results. In addition, there was consistent evidence that the aircraft encountered ground effect at a height above one wing span.
The theory of functionals is used to reformulate the notions of aerodynamic indicial functions and superposition. Integral forms for the aerodynamic response to arbitrary motions are derived that are free of dependence on a linearity assumption. Simplifications of the integral forms lead to practicable nonlinear generalizations of the linear superposition and the stability derivative formulations. Applied to arbitrary nonplanar motions, the generalization yields a form for the aerodynamic response that can be compounded of the contributions from a limited number of well-defined characteristic motions, in principle reproducible in the wind tunnel. Further generalizations that would enable the consideration of random fluctuations and multivalued aerodynamic responses are indicated.