Analysis of Linear Dynamic Systems
John B. Lewis, Hector Saunders · Journal of Mechanical Design · 1981
phenomena and involves inertial, elastic, and aerodynamic forces.Previously, aeroelasticity was in the private domain of aeronautical applications.In recent years, aeroelasticity has expanded to mechanical engineering, i.e. flows around turbomachinery and compressor blades, fluid flow in pipes; nuclear energy, i.e. flow about fuel elements and heat exchanger tubes; civil engineering, i.e. flow about tall buildings, bridges, and chimney stacks.The book consists of eight chapters and one main appendix which is a primer on random pressure fluctuations.The first four chapters entail basic information of aeroelasticity and is written by the editor.The remaining four chapters are written by the other three coauthors.Chapter I is an introduction and Chapter II discusses static aeroelasticity.This chapter considers the various forms of static aeroelasticity, i.e. divergence, one-dimensional aeroelastic model of airfoils, rolling of a straight wing, aeroelastic equation of equilibrium, reversal and rolling effectiveness of a wing and concludes with the fluid through a flexible pipe.Chapter III initiates the reader into dynamic aeroelasticity.Beginning with the basic Hamilton's principle and Lagrange's equation, we venture forth into dynamic aeroelastic instability, supersonic flutter, including an introduction to piston theory, transonic buzz with a brief mention of strip theory employed in flutter analysis.A good discussion of gust loading leads into random vibration analysis and its applications.The chapter concludes with an introduction to panel flutter and a more detailed discussion of fluid flow through a flexible pipe.The reviewer believes that the section on strip theory and application of the use of Mach boxes was too brief.Chapter IV dwells upon nonsteady aerodynamics of lifting and nonlifting surfaces.Initially, the basic fluid dynamic equations are considered, which then lead to the more advanced aspects of supersonic flow (two-dimensional) transitional motion, lift due to aerodynamic gust, and then into three-dimensional flow (incompressible and compressible).The classic Theodorsen's F and G functions, Wagner's, and Kussner's functions are derived and employed in the lift equations.The newer methods used in transonic flow are considered in light of the failure of classic linear perturbation theory.They are Spreiter's "local linearization," Landhal's "parametric linearization," and Dowell's approximation methods.Comparing experiments and theory, the newer methods are in fairly good agreement.Chapter V considers stall flutter in the sense of a nonlinear aerodynamic reaction to the motion of the airfoil structure.This is slanted towards the static type (nonrotating) and applied to aircraft wings and tail surfaces plus the "galloping" of electric power transmission cables of circular cross section.The new theory of Sisto and Perumal is supposed to explain stall flutter analytically and not rely completely upon experimental data.Although promising, much work remains to put this theory into the repertoire of useful known procedures of the aeroelasticians.Chapter VI introduces the Tacoma Narrows bridge failure as an introduction to aeroelasticity in civil engineering applications.The prime interests of the latter reside in divergence, galloping due to bodies acted upon by a wind force.This, in turn, is divided into across-wind and wakeinduced flow.The former is exemplified by ice-coated power lines under wind and the latter is illustrated by flow over a bundled-conducted power line.Vortex shedding plays a role in causing oscillations of tall unsupported stacks and towers which exhibit "Aeolian" vibrations.Other important occurrences are torsional type flutter of open sections and buffeting of building towers and structures.Chapter VII concerns itself with aeroelastic problems or rotorcraft.This includes blade dynamics, stall flutter,