Transonic aeroelastic solutions based upon the transonic small perturbation potential equation were studied. Time-marching transient solutions of plunging and pitching airfoils were analyzed using a complex exponential modal identification technique, and seven alternative integration techniques for the structural equations were evaluated. The HYTRAN2 code was used to determine transonic flutter boundaries versus Mach number and angle-of-attack for NACA 64A010 and MBB A-3 airfoils. In the code, a monotone differencing method, which eliminates leading edge expansion shocks, is used to solve the potential equation. When the effect of static pitching moment upon the angle-of-attack is included, the MBB A-3 airfoil can have multiple flutter speeds at a given Mach number.

/pdf/time-marching-transonic-flutter-solutions-including-angle-of-2d7gr7ddeb.pdf

Time-marching transonic flutter solutions including angle-of-attack effects

Since emphasis is on the transonic speed range, special importance is placed on configurations for which available data are sufficient to define accurately a transonic flutter boundary. Only configurations with clean, smooth surfaces are considered suitable. Segmented models or models with surface-slope discontinuities are inappropriate. Excluded also, in general, are configurations and data sets that involve behavior that is uncertain or not well understood, uncertain model properties, or know sensitivities to small variations in model properties. In order to assess the suitability of configurations already tested and the associated data for designation as standard, a survey of AGARD member countries was conducted to seek candidates for the prospective set. The results of that survey are given and summarized along with the initial selection of a standard configuration.

https://ntrs.nasa.gov/api/citations/19890009875/downloads/19890009875.pdf

AGARD standard aeroelastic configurations for dynamic response

Computational methods for unsteady transonic flows are surveyed with emphasis on prediction. Computational difficulty is discussed with respect to type of unsteady flow; attached, mixed (attached/separated) and separated. Significant early computations of shock motions, aileron buzz and periodic oscillations are discussed. The maturation of computational methods towards the capability of treating complete vehicles with reasonable computational resources is noted and a survey of recent comparisons with experimental results is compiled. The importance of mixed attached and separated flow modeling for aeroelastic analysis is discussed, and recent calculations of periodic aerodynamic oscillations for an 18 percent thick circular arc airfoil are given.

/pdf/computational-methods-for-unsteady-transonic-flows-3qbqhi6v0b.pdf

Computational methods for unsteady transonic flows

A review of scale effects in unsteady aerodynamics

Effects of transition on wind tunnel simulation of vehicel dynamics

A wind-tunnel flutter test on a supercritical wing model is described. Objectives of the test were to investigate the transonic dip and to make comparisons with calculated flutter characteristics in which a quasi-threedimensional transonic theory was used. The beginning of a transonic dip was measured and a satisfactory agreement with theory could be found. An additional flutter instability in the bottom of the transonic dip could be correlated with the loss of transition strip effectivity at low Reynolds numbers. Nomenclature a,b = correction factors [Eqs. (2)] c =chord Clo = sectional steady lift coefficient CL - wing lift coefficient / = frequency g = damping coefficient k = reduced frequency (related to semichord) k - sectional unsteady lift coefficient, k2D, k3D m = sectional unsteady moment coefficient (related to quarterchord), m2D, m3D MO, = Mach number P0 = stagnation pressure q = generalized coordinate Rec = Reynolds number related to mean aerodynamic chord xt = position of transition strip a = wing angle of incidence A = (mean) sweep angle

Wind-Tunnel Study of the Flutter Characteristics of a Supercritical Wing

A wind-tunnel flutter test on a supercritical wing model is described. Objectives of the test were to investigate the transonic dip and to enable comparisons with calculated flutter characteristics in which a quasi-3-D transonic theory was used. The beginning of a transonic dip was measured and a satisfactory agreement with theory could be found.
An additional flutter instability in the bottom of the transonic dip could be correlated with the loose of transition strip effectivity at low Reynolds numbers.

A. N. Kraan

Papers

Wind-Tunnel Study of the Flutter Characteristics of a Supercritical Wing

A wind-tunnel study of the flutter characteristics of a supercritical wing