Lateral oscillations occurring on the aircraft model of NASA TP 1803 at angles of attack ranging from 25 deg of angle to 60 deg of angle have been investigated in a low-speed wind tunnel for configurations including fuselage with wing or with a combination of wing and leading-edge extension (LEX). The wind tunnel experiment was conducted in the range of Mach number from 0.1 to 0.2, and the range of the Reynolds number based on the body diameter from 2.8 x 105 to 5.6 x 105. The time-varying side force coefficients, which may represent the displacements of oscillation in the lateral direction, were measured to obtain the root-mean-square values and the power spectra. Flow visualization of the vortices generated from the forebody, wing and LEX of the model has also been performed in a water tunnel. It was found that the entire system of the flow and the sting-supported model locks-in at the resonant oscillation frequency as the lateral oscillation occurs. The presence of LEX significantly enhances the oscillation amplitude especially at high enough angles of attack, i.e. alpha > 40 deg of angle. The enhancement of the lateral oscillation, as suggested by the water tunnel visualization, seems closely related to the breakdown of the LEX vortices in general and the location of breakdown in particular. The power spectra of the test model with wind and LEX exhibit a transition from weakly nonlinear to broad band oscillations as alpha is increased from 45 deg of angle to 60 deg of angle. The appearance of a broead range of frequencies around or below the dominant frequency, that can be indicative of possible chaotic oscillation, corresponds to a sharp drop of the lateral oscillation amplitude. The effect of Reynolds number is notable only at alpha > 50 deg of angle. Variation of the sideslip angle between 0 deg of angle and 10 deg of angle appears to have no discernible effects on the amplitude of lateral oscillation for the test model with wing and LEX.
Lateral oscillations of an aircraft model at high angles of attack
Querschwingungen eines Flugzeugmodells bei großen Anstellwinkeln
Journal of Fluids and Structures ; 10 , 6 ; 601-614
1996
14 Seiten, 15 Bilder, 16 Quellen
Article (Journal)
English
Aerodynamik , Querschwingung , Windkanal , Versuchsmodell , Anstellwinkel (Tragflügel) , Strömungsgeschwindigkeit , Flugzeugrumpf , Mach-Zahl , Reynolds-Zahl , Seitenkraft , Zeitverhalten , Methode der kleinsten Quadrate , Wirbelströmung , Wasserkanal , Resonanzfrequenz , Nichtlinearität , Strömungsvisualisierung
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