Static Aeroelastic Effects Research Articles

Design load predictions on a fighter-like aircraft wing

Numerical solutions for a transonic design condition have been obtained for a fighter-like aircraft wing geometry using Euler and Navier-Stokes equations. Both rigid and flexible wings are considered. Effects of viscosity and static aeroelasticity on the component loads such as shear, bending moment, and torsion, as well as hinge moments on the flaps and ailerons, are predicted. The flexible wing solutions are obtained by coupling the flow solvers with a simple NASTRAN model. Effects of fuselage and horizontal tail have also been obtained for the rigid wing case using Euler equations. The computed results are compared to available flight test data. It is found that the static aeroelasticity has only a minor role, whereas the effect of viscosity is very pronounced. Comparison with the flight test data is found to be best when viscous effects are included.

Integrating nonlinear aerodynamic and structural analysis for a complete fighter configuration

The coupling of a nonlinear aerodynamics program with a structural analysis program to include the effects of static aeroelasticity in early preliminary design studies is described. A nonlinear, full potential aerodynamics method with capability to model geometric details of a complete aircraft in supersonic flow is used. The deflections of the lifting surfaces are calculated using an equivalent plate structural representation which can readily accommodate the changes in stiffness and geometric properties required during the preliminary design process. An iterative solution procedure is used to obtain consistent aerodynamic loads and structural deflections at the specified flight conditions. The volume of data transmitted between programs is minimized. The procedure is applied to a complete aircraft and the numerical results illustrate the aeroelastic effects on pressure distribution as well as total forces and moments. During this design study, the thickness distribution of the wing cover skins was initially sized based on rigid loads and subsequently resized under aeroelastic loads. Comparisons are made between these nonlinear aeroelastic results and results obtained from linear aerodynamic methods applied to a rigid shape during conceptual design studies.

Static aeroelastic characteristics of circulation control wings

Circulation control airfoils can develop lift coefficients far in excess of conventional airfoils through the use of tangential blowing and thus have potential applications for V/STOL aircraft. The static aeroelastic effects of circulation control on swept wings are examined using two analytical models: a simple two-degree-of-freedom model with linearized aerodynamics and an elastic beam model coupled with nonlinear two-dimensional airfoil data. The static divergence instability and a circulation control reversal phenomenon are investigated through the use of lift and control effectiveness ratios. Effects of wing sweep angle, elastic axis location, blowing level, and spanwise blowing distribution are presented. Linear, nonlinear incompressible, and nonlinear compressible aerodynamic representations are compared. Significant differences were observed between the linear and nonlinear aerodynamic results. Tailoring of the spanwise blowing distribution is shown to be an effective means of improving undesirable aeroelastic characteristics. The results indicate that the aeroelastic behavior of circulation control wings can be quite different from that of conventional wings.

Static aeroelastic twist effects on helicopter rotor-induced velocity

Static aeroelastic twist effects on helicopter rotor-induced velocity

Evaluation of Techniques for Predicting Static Aeroelastic Effects on Flexible Aircraft

An experimental evaluation of analytical techniques for predicting the longitudinal stability characteristics of a large flexible aircraft is presented. Analytical methods based on both the modal approach and stiffness influence coefficients are used to predict the aerodynamic characteristics of a flexible airplane. These methods are then applied to a flexibly scaled model of a supersonic transport configuration. Comparisons between wind-tunnel data, the modal approach, and calculations based on stiffness influence coefficients are presented over the Mach number range from M = 0.6-2.7. The results of this study show good agreement for most cases between analyses and experiment. Nomenclature a.c. = aerodynamic center position Aa.c. = shift in aerodynamic center position due to flexibility, positive forward b — wing span c = local chord measured streamwise c = reference chord CL = lift coefficient, lift/gS CLx = lift-curve slope, 8CL/dot at a = 0° CL | a =o = lift coefficient at a = 0° CLq = lift coefficient due to pitching, 8CL/d(9c/2V) CL5e = elevator effectiveness in lift, dCL/88e