Aeroelastic Dynamics Research Articles

Design of Efficient Partitioned Procedures for the Transient Solution of Aeroelastic Problems

ABSTRACT We consider the problem of solving large-scale non-linear dynamic aeroelasticity problems in the time-domain using a fluid-structure partitioned procedure. We present a mathematical framework for assessing some important numerical properties of the chosen partitioned procedure, and predicting its performance for realistic applications. Our analysis framework is based on the estimation of the energy that is artificially introduced at the fluid-structure interface by the staggering process that is inherent to most partitioned solution methods. This framework provides a powerful means for the construction of more accurate and stable partitioned methods. Using two- and three-dimensional, transonic and supersonic, wing and panel aeroelastic applications, we validate this framework and highlight its impact on the design and selection of a staggering algorithm for the solution of coupled fluid-structure equations.

Comparison of µ- and H-Synthesis Controllers 2 on an Experimental Typical Section

An experimental comparison of H2- and π-synthesized e utter suppression control systems was performed. A simpleparametric uncertainty can beused to track changesin system dynamics asa function of dynamicpressure. The control system was implemented experimentally on a NACA 0012 test model of a typical section mounted in a low-speed wind tunnel. The pitching angle, e ap angle, and plunge dee ection of the airfoil were measured with sensorsand fed back through the control compensator to generatea single control signal commanding the trailingedge e ap of the airfoil. The model of the aeroelastic system, including the dynamics of the sensors and actuators in the bandwidth of interest, was obtained using system identie cation techniques. For comparison purposes, an H2 control system with standard linear quadratic Gaussian weightings also was designed and implemented. When compared to the H2 control system, the π-synthesis controller provided better disturbance rejection in the bandwidth of the unsteady aeroelastic dynamics. In addition, the π controller required less control energy than the H2 control system. The e nal advantage of π-synthesis is the ability to design an aggressive π control system that is stabilizing across the range of operating dynamic pressures.

Static and Dynamic Aeroelasticity of Advanced Aircraft Wings Carrying External Stores

A study of the static and dynamic aeroelasticity of aircraft wings carrying external stores is presented. The wing structure is modeled as a laminated composite plate exhibiting flexibility in transverse shear and including warping restraint effects. The relevant equations of motion and boundary conditions are obtained via Hamilton's variational principle and application of generalized function theory. To achieve a realistic representation of the store influence on static and dynamic behavior of the system, static weights, as well as dynamic inertias of the stores, are considered. For the problem at hand, three-dimensional strip theory aerodynamics is employed. The obtained eigenvalue/boundary value problems are being solved by application of the extended Galerkin method. The solution procedure is used to investigate the implications of external stores on static aeroelastic response, divergence, free vibration, and flutter. Comparisons with the very few results highlighting the effects of underwing and tip stores on flutter instability are carried out, and excellent agreements with the present predictions are reported.

Static and dynamic aeroelasticity of advanced aircraft wings carrying external stores

Static and dynamic aeroelasticity of advanced aircraft wings carrying external stores

Pilot modeling and closed-loop analysis of flexible aircraft in the pitch tracking task

The issue addressed in the appropriate modeling technique for pilot vehicle analysis of large flexible aircraft, when the frequency separation between the rigid-body mode and the dynamic aeroelastic modes is reduced. This situation was shown to have significant effects on pitch-tracking performance and subjective rating of the task, obtained via fixed base simulation. Further, the dynamics in these cases are not well modeled with a rigid-body-like model obtained by including only 'static elastic' effects, for example. It is shown that pilot/vehicle analysis of this data supports the hypothesis that an appropriate pilot-model structure is an optimal-control pilot model of full order. This is in contrast to the contention that a representative model is of reduced order when the subject is controlling high-order dynamics as in a flexible vehicle. The key appears to be in the correct assessment of the pilot's objective of attempting to control 'rigid-body' vehicle response, a response that must be estimated by the pilot from observations contaminated by aeroelastic dynamics. Finally, a model-based metric is shown to correlate well with the pilot's subjective ratings.

Effects of Dynamic Aeroelasticity on Aircraft Handling Qualities

Body Combinations, Discussions by J.P. Giesing, Analytic Methods in Aircraft Aerodynamics, NASASP-228, 1969. Hink, G.R., Bills, G.R., and Dornfeld, G.M., A Method for Predicting the Characteristics of Control Configured Vehicles. Vol. H-Flexstab User's Manual, Air Force Flight Dynamics Laboratory, Wright-Patterson Air Force Base, Ohio, Rept. AFFDL-TR-74-91,Nov. 1974. Dillenius, M.F.E. and Nielsen, J.N., Prediction of Aerodynamics of Missiles at High Angles of Attack in Supersonic Flow, Nielsen Engineering and Research, Inc., Mountain View, Calif., Rept. NEAR TR-99, Oct. 1975. Lan, C.E., Calculation of Lateral-Directional Derivatives for Wing-Body Combinations With and Without Jet Interaction Effects, NASA CR-145251,1977. Lan, C.E., A Quasi Vortex-Lattice Method in Thin Wing Theory, Journal of Aircraft, Vol. 11, Sept. 1974, pp. 518-527. Lan, C.E. and Mehrotra, S.C., An Improved Woodward's Panel Method for Calculating Leading-Edge and Side-Edge Suction Forces, The University of Kansas Center for Research, Inc., Lawrence, Kansas, Tech. Rept. CRINC-FRL-266-3, Feb., 1979. Lamar, J.E., Extension of Leading-Edge-Suction Analogy to Wings with Separated Flow Around the Side Edges at Subsonic Speeds, NASA TR R-428, Oct. 1974. Margolis, K., Theoretical Calculations of the Lateral Force and Yawing Moment Due to Rolling at Supersonic Speeds for Sweptback Tapered Wings with Stream wise Tips. Subsonic Leading Edges, NACATN 2122, June 1950. Harmon, S.M., Stability Derivatives at Supersonic Speeds of Thin Rectangular Wings with Diagonals Ahead of Tip Mach Lines, NACA Rept. 925, 1949. flying qualities, such effects should not be overlooked in calculations or analyses directed toward investigation of compliance with the requirements of this specification. The specification is concerned mainly with desirable ranges of values on rigid body static and dynamic response parameters. There are methods available for estimating static aeroelastic corrections to rigid body aerodynamic stability derivatives; however, these are then used in rigid aircraft equations of motion. It seems quite possible that the desirable ranges of parameter values could be significantly affected by elastic mode degrees of freedom—particularly when some of the modes have natural frequencies of the same order of magnitude as the frequencies of the rigid body alone. It is not clear at all that the handling qualities should be specified by rigid body dynamic parameters when such mode interaction is present. In fact, the pilot would find it difficult to tell, for example, how much of a given pitch angle response to command input is due to rigid body and how much to lowfrequency elastic modes.

Some problems of vibration and stability of shells and plates

Considered are problems of free and forced vibrations, static and dynamic stability and aeroelasticity of orthotropic shells and plates placed in a variable temperature field. It is assumed that the physical-mechanical characteristics of the material of the shell (plate) depend on the temperature.It is shown that taking into account the dependence of the physical-mechanical properties of the material of the shell (plate) on temperature introduces essential qualitative and quantitative changes in the problem of vibration and stability.

DYNAMIC STABILITY AND AEROELASTIC CONSIDERATIONS IN THE DESIGN OF LARGE STEERABLE ANTENNAS*

Annals of the New York Academy of SciencesVolume 116, Issue 1 p. 311-323 DYNAMIC STABILITY AND AEROELASTIC CONSIDERATIONS IN THE DESIGN OF LARGE STEERABLE ANTENNAS* Frederick H. Hull, Frederick H. Hull North American Aviation, Inc., Columbus Division, Columbus, OhioSearch for more papers by this author Frederick H. Hull, Frederick H. Hull North American Aviation, Inc., Columbus Division, Columbus, OhioSearch for more papers by this author First published: June 1964 https://doi.org/10.1111/j.1749-6632.1964.tb33949.x * Parts of this work were performed under subcontract with MIT/LL which operated with support from the U. S. Army, Navy and Air Force. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Volume116, Issue1Large Steerable Radio Antennas-Climatological and Aerodynamic ConsiderationsJune 1964Pages 311-323 RelatedInformation