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National Advisory Committee for Aeronautics, Technical Notes - Effects of Boundary Layer Displacement and Leading Edge Bluntness on Pressure Distribution, Skin Friction and Hear Transfer of Bodies at Hypersonic Speeds

Aerodynamic forces and moments associated with flapping oscilla-
tions of finite wings at low speeds are considered. A comparison of
theoretical and experimental results is made for a rectangular wing of
aspect ratio 2. Calculated results are also given for three tapered
wings of aspect ratio 5 with varying amounts of sweepback. The calcu—
lations are based on a numerical solution of the integral equation of
subsonic lifting—surface theory. The experimental techniques employed
are essentially those used in previous measurements associated with
pitching oscillations. Theory and experiment are generally in good
agreement with regard to magnitude of the forces and moments, but dif-
fer with regard to phase angle.

Until recently the treatment of the aerodynamic portion of the
flutter problem has been based primarily on the two-dimensional theory
of oscillating wings. Generalized aerodynamic coefficients required
for flutter analysis have normally been obtained by various strip—
analysis methods in which two-dimensional section coefficients associated
with rigid mode displacements, such as translation and pitch, are used
together with actual spanwise variations in displacement. With the
increasing need for more accurately predicted flutter boundaries, however,
attempts have been made to obtain more accurately the aerodynamic come
ponents of the flutter problem. Considerable effort has been directed
toward the experimental measurement of oscillatory aerodynamic forces
and moments. In reference 1, for example, measured forces and moments
are presented for the case of pitching oscillations for one of the con-
figurations dealt with in the present investigation.

Efforts have also been made in the direction of increasing accuracy
in the theoretical determination of oscillatory aerodynamics. With the
aid of advances in high-speed computing equipment, procedures have been
developed for obtaining the aerodynamic forces associated with the par-
ticular plan form of interest and with its specific modes of oscilla-
tion. One such procedure, a numerical solution of the integral equation
of subsonic lifting-surface theory, is described in reference 2. A
more recent, related procedure developed in the Iangley Flutter Analysis
Section has been employed in the present investigation.