Transonic single-mode flutter and buffet of a low aspect ratio wing having a subsonic airfoil shape
National Aeronautics and Space Administration, 1974 - Technology & Engineering - 19 pages
Transonic 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 angle of attack ASPECT RATIO WING autocorrelation bending and torsion bending gage bending moments boundary boundary-layer trips buffet onset angle damping ratios degree of freedom delta wing dynamic pressure dynamic response elastic axis fiberglass flutter and buffet flutter behavior flutter motion flutter occurred free-stream frequency spectra full scale gage gage gage higher Mach number instabilities layer trips leading edge low aspect ratio Mach number range mass ratio maximum buffet intensity NACA 00XX-64 airfoil narrow Mach number NASA normal mode frequency normal mode vibration number range centered numbers from 0.6 occurred at angles oscillograph peak planform Random Vibration reduced frequency 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 total pressure trailing edge transonic flutter trips removed variation Wind Tunnel wing motion wing root bending wing tip zero lift flutter