Effects of viscosity and modes on transonic aerodynamic and aeroelastic characteristics of wings

The research reported in this paper is concerned with aerodynamic and aeroelastic computations in the transonic regime. The aerodynamic computations were made using small-disturbance, unsteady, transonic theory with viscous corrections. New areas of investigation included studying the effects of viscous corrections on the aerodynamics about wings and the effect of including higher structural modes in addition to the fundamental bending and torsion modes in transonic aeroelastic analyses. Two wings were studied, a rectangular wing, with a NACA 64A010 airfoil section, and a swept wing, with an MBB-A3 supercritical airfoil section. Viscous effects on both wings were analyzed by employing the viscouswedge and lag-entrainment methods. Aeroelastic analyses were performed and the effects of including the first two bending and torsion modes into the analysis are shown. Also discussed are the practical aspects of generating unsteady, transonic aerodynamic coefficients. Results from this work show that the inclusion of viscous effects increases the flutter speed for the two wings studied. For the rectangular wing, the fundamental modes were sufficient to determine the flutter speed, but the second torsion mode was required for an accurate aeroelastic analysis of the swept wing. These studies can aid aeroelasticians in selecting viscous methods and also structural modes to conduct aeroelastic analyses in the transonic regime.