Angle-of-Attack Effect on Transonic/Supersonic Aeroelasticity of Wing-Box Model

Abstract

N understanding of the aeroelastic behavior of e ight vehicles in the transonic and low-supersonic regimes is of great importance for e ight safety. The e utter boundary in this regime varies with changes in the initial angle of attack. Aeroelastic analyses and experiments on the effect of initial angle of attack have been performed previously. Early studies of the two-degree-of freedom airfoil system were performed using the HYTRAN2 (Ref. 1) and an Euler code. 2 For a three-dimensional wing at high angles of attack in incompressible e ow, there is the work by Strganac and Mook. 3 In their paper, using the unsteady vortex-lattice method, the equations of motion were integrated, considering the nonlinear effects of the separated vortex. Yates et al. 4 analyzed the effect of angle of attack on a large aspect ratio transport-type wing with a supercritical airfoil, using a modie ed strip analysis employing wind-tunnel steady aerodynamic data. Also, the CAP-TSD code 5 has been applied to the active e exible wing wind-tunnel model to investigate static and dynamic aeroelastic behaviors below Mach 0.95. These studiesprovideagoodfoundationforunderstandinginitialangle-ofattack effects, both theoretically and practically, and motivated by this,wewillexamineindetailtheeffectofbothpositiveandnegative angles of attack on a typical e ghter wing-box model with an asymmetric airfoil in the transonic and low-supersonic e ow regions. The critical effect of a negative angle of attack and unusual frequency changes due to the effect of normal shocks are presented. The computed steady aerodynamic results for rigid and deformed shapes of the model are presented and compared. Also, detailed dynamic aeroelastic responses are computed using a coupled time-marching method based on the effective computational structural dynamic (CSD) and computational e uid dynamic (CFD) techniques, 6 which are similar to those used in Ref. 5. CSD analyses for the wing-box model have beenperformed using MSC/NASTRAN.Thevariations