Transonic Single-mode Flutter and Buffet of a Low Aspect Ratio Wing Having a Subsonic Airfoil ShapeTransonic flutter and buffet results obtained from wind-tunnel tests of a low aspect ratio semispan wing model are presented. The tests were conducted to investigate potential transonic aeroelastic problems of vehicles having subsonic airfoil sections. The model employed NACA 00XX-64 airfoil sections in the streamwise direction and had a 14 deg leading edge sweep angle. Aspect ratio, and average thickness were 4.0, 0.35, and 8 percent, respectively. The model was tested at Mach numbers from 0.6 to 0.95 at angles of attack from 0 deg to 15 deg. Two zero lift flutter conditions were found that involved essentially single normal mode vibrations. With boundary layer trips on the model, flutter occurred in a narrow Mach number range centered at about Mach 0.90. The frequency and motion of this flutter were like that of the first normal mode vibration. With the trips removed flutter occurred at a slightly high Mach number but in a mode strongly resembling that of the second normal mode. |
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40 percent chord aerodynamic damping aeroelastic angles of attack ASPECT RATIO WING autocorrelation bending and torsion bending gage bending moments Birch spar boundary layer boundary-layer trips buffet onset angle damping at atmospheric damping ratios delta wing dynamic pressure elastic axis fiberglass figure 17 flutter and buffet flutter motion flutter occurred frequency spectra full scale gage gage gage higher Mach number instabilities k₁ kN/m² layer trips leading edge low aspect ratio Mach number range mass ratio maximum buffet intensity N/m² NACA 00XX-64 airfoil narrow Mach number NASA normal mode frequency normal mode vibration number range centered numbers from 0.6 P₁ peak pitching moment planform second mode second normal mode separated flow shock stall shown in figure Space Shuttle spanwise stall flutter static Still-air damping strain-gage signals SUBSONIC AIRFOIL tongue torsion gage signals total pressure transonic flutter trips removed Wind Tunnel wing motion wing tip zero lift flutter