Static Aeroelastic Effects on the Flutter of a Supercritical Wing,
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION HAMPTON VA LANGLEY RESEARCH CEN TER
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It is well known that wings with supercritical airfoils generally have lower transonic flutter speeds than similar wings with conventional airfoils and that small increases in angle of attack from zero and the accompanying static aeroelastic deformations have further detrimental effects on transonic flutter. This paper presents results of an effort to calculate the effects of angle of attack and the associated aeroelastic deformation on the flutter of a highly swept supercritical wing TF-8A by use of modified strip analysis. The spanwise distributions of steady-state section life-curve slope and aerodynamic calculations for as input for these calculations were obtained from static aeroelastic calculations for the wing by use of hte FL022 transonic code and an assumed dynamic pressure. The process is iterative so that flutter can be obtained at the same dynamic pressure as that used to calculate the statically deformed shape and loading about which the flutter oscillation occurs matched conditions. Investigation results show that the unconventional backward turn of the transonic dip in the experimental flutter boundary for angles of attack greater than zero is caused by variations in mass ratio and not by static aeroelastic deformation, although inclusion of the latter appears to be required for quantitative accuracy in the calculations. For the very high subsonic Mach numbers of this investigation, quantitative accuracy will also require inclusion of viscous effects on shock strength and location.