A Method for Stabilizing Shock Waves in Channel Flow by Means of a Surge Chamber
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Neice, Stanford E↗
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Preliminary theoretical investigation of several methods for stabilizing the lateral motion of a high-speed fighter airplane towed by a single cable
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Schy, Albert A↗
Introduction to Computational Methods for Stability and Control (COMSAC)
This Symposium is intended to bring together the often distinct cultures of the Stability and Control (S&C) community and the Computational Fluid Dynamics (CFD) community. The COMSAC program is itself a new effort by NASA Langley to accelerate the application of high end CFD methodologies to the demanding job of predicting stability and control characteristics of aircraft. This talk is intended to set the stage for needing a program like COMSAC. It is not intended to give details of the program itself. The topics include: 1) S&C Challenges; 2) Aero prediction methodology; 3) CFD applications; 4) NASA COMSAC planning; 5) Objectives of symposium; and 6) Closing remarks.
Hall, Robert M.↗
Comparison of several methods for estimating low speed stability derivatives
Methods presented in five different publications have been used to estimate the low-speed stability derivatives of two unpowered airplane configurations. One configuration had unswept lifting surfaces, the other configuration was the D-558-II swept-wing research airplane. The results of the computations were compared with each other, with existing wind-tunnel data, and with flight-test data for the D-558-II configuration to assess the relative merits of the methods for estimating derivatives. The results of the study indicated that, in general, for low subsonic speeds, no one text appeared consistently better for estimating all derivatives.
Fletcher, H. S.↗
Magnets with stabilized conductors
Method fabricates stabilized composite conductor, for use in construction of magnets, using equal amounts of superconducting and metal materials, thus reducing weight, cost and size.
Jones, C. K.↗
Experimental transition and boundary-layer stability analysis for a slotted swept laminar flow control airfoil
A swept, supercritical laminar flow control (LFC) airfoil designated NASA SCLFC(1)-0513F was tested at subsonic and transonic speeds in the NASA Langley eight-foot Transonic Pressure Tunnel. This paper examines Tollmien-Schlichting and crossflow disturbance amplification for this airfoil using the linear stability method. The design methodology using linear stability analysis is evaluated and the results of the incompressible and compressible methods are compared. Experimental data on the swept, supercritical LFC airfoil and reference wind tunnel and flight results are used to correlate and evaluate the N-factor method for transition prediction over a speed range M(infinity) from zero to one.
Harvey, William D.↗
Stability of a dual-spin spacecraft with spherical dampers
The present investigation is concerned with the stability characteristics of a specific dual-spin satellite configuration marked by a high degree of symmetry. The configuration includes a platform and a rotor. Both components contain arbitrarily located internal spherical dampers. The symmetry of the system configuration makes it possible to illustrate clearly the relationship between Routhian analysis, energy sink analysis, and digital simulation of the full nonlinear equations. Although the dual-spin spacecraft configuration contains energy dissipating devices on both platform and rotor, it is still possible to employ the rigorous, but relatively simple, Routh stability method. This method, unlike Floquet theory, has the potential of producing closed-form stability criteria. The energy sink method is capable of providing a closed-form stability criterion. Numerical simulation is a necessary requirement in the latter stages of design when the realistic perturbation environment must be considered.
Laskin, R. A.↗
An analysis of methods for predicting the stability characteristics of an elastic airplane. Appendix B - Methods for determining stability derivatives
Stability derivatives for predicting stability characteristics of elastic aircraft
Source record↗
Stability theory of multistep methods
Numerical solution of differential equations using predictor-corrector multistep methods for stability theory
STABILITY↗
Two new methods for obtaining stability derivatives from flight test data
New methods for obtaining stability derivatives from flight data
Burgin, G. H.↗
A comparison of two methods of extracting stability derivatives from flight test data
Two methods for extracting stability derivatives from flight data are compared. A modified Newton-Raphson quasilinearization minimization technique and a digital-analog (hybrid) matching technique were used to analyze the same data maneuvers obtained from two aircraft. About 70 maneuvers from an F-111E aircraft were analyzed over a Mach number range of 0.3 to 2.0 and an angle of attack range of 3 to 19 degrees. About 20 maneuvers were analyzed for the X-24A lifting body at Mach numbers of 0.5, 0.8, and 0.9, and an angle of attack range of 4 to 13 degrees. Stability derivatives were extracted from these maneuvers and the results from the two techniques, along with wind tunnel results, were compared.
Kirsten, P. W.↗
Methods of predicting helicopter stability
Some of the methods of predicting rotor stability derivatives have been reviewed. The methods by which these rotor derivatives are employed to estimate helicopter stability characteristics have been summarized. It is concluded that, although these methods are not always feasible for predicting absolute values of the stability of the helicopter, the effects on stability of changes in individual derivatives can generally be estimated satisfactorily.
Robert J Tapscott↗
System and method for determining stability of a neural system
Disclosed are methods, systems, and computer-readable media for determining stability of a neural system. The method includes tracking a function world line of an N element neural system within at least one behavioral space, determining whether the tracking function world line is approaching a psychological stability surface, and implementing a quantitative solution that corrects instability if the tracked function world line is approaching the psychological stability surface.
Curtis, Steven A.↗
Symmetric and nonsymmetric buckling of finitely deformed eccentrically stiffened shells of revolution.
Finite difference method stability analysis of deformed eccentrically stiffened shells of revolution, accounting for finite prebuckling rotations
FINITE DIFFERENCE METHOD↗
Rotation in vibration, optimization, and aeroelastic stability problems
The effects of rotation in the areas of vibrations, dynamic stability, optimization, and aeroelasticity were studied. The governing equations of motion for the study of vibration and dynamic stability of a rapidly rotating deformable body were developed starting from the nonlinear theory of elasticity. Some common features such as the limitations of the classical theory of elasticity, the choice of axis system, the property of self-adjointness, the phenomenon of frequency splitting, shortcomings of stability methods as applied to gyroscopic systems, and the effect of internal and external damping on stability in gyroscopic systems are identified and discussed, and are then applied to three specific problems.
Kaza, K. R. V.↗
The modified equation approach to the stability and accuracy analysis of finite-difference methods
The stability and accuracy of finite-difference approximations to simple linear partial differential equations are analyzed by studying the modified partial differential equation. Aside from round-off error, the modified equation represents the actual partial differential equation solved when a numerical solution is computed using a finite-difference equation. The modified equation is derived by first expanding each term of a difference scheme in a Taylor series and then eliminating time derivatives higher than first order by certain algebraic manipulations. The connection between 'heuristic' stability theory based on the modified equation approach and the von Neumann (Fourier) method is established. In addition to the determination of necessary and sufficient conditions for computational stability, a truncated version of the modified equation can be used to gain insight into the nature of both dissipative and dispersive errors.
Warming, R. F.↗
Design concepts using ring lasers for frequency stabilization
Laser frequency stabilization methods are based on a frequency discriminant which generates an unambiguous deviation signal used for automatic stabilization. Closed-loop control stabilizes cavity length at a null point. Some systems have a stabilized ring laser using a piezoelectric dither and others use a Doppler gain tube.
Mocker, H.↗
Autoionization: Recent developments and applications
Among the topics discussed are: theory of resonance and autoionization of two-electron atoms and ions; projection and quasi-projection operators for electron impact resonances on many-electron atomic targets; and hole projection methods for calculating Feshbach resonances and inner-shell vacancies. Consideration is also given to: complex stabilization methods; complex coordinate and complex basis function calculations; and the variational principle. The application of autoionization calculations to solar and astrophysical plasma diagnostics is also discussed in detail.
Temkin, A.↗