Nonlinear aeroelastic analysis is essential for high-altitude long-endurance (HALE) aircraft. In the current paper, we have presented a computational aeroelastic tool for nonlinear-aerodynamics/nonlinear-structure interaction. Specifically, a consistent nonlinear time-domain aeroelastic methodology has been integrated via tightly coupling a geometrically exact nonlinear intrinsic beam model and the generalized unsteady vortex-lattice aerodynamic model with vortex roll-up and free wake. The effects of discrete gust as well as flow separation at various angles of attack from attached flow to the stall and poststall ranges are also included in the nonlinear aerodynamic model. A HALEwing model is analyzed as a numerical example. The trim angle of attack is first found for the wing, and the results show that aeroelastic instability could occur at higher angles of attack. The HALE-wing model under the trim condition is then analyzed for various gust profiles to which it is subject. It is found that for certain gust levels, the elastic deformations of the HALE wing tend to become unstable: notably, the in-plane deflections become very significant. It is noted for the unstable solution of the HALE wing that the flow may be well beyond the stall range. An engineering approach with the use of the nonlinear sectional lift is attempted to consider such stall effects.

The morphing of an air vehicle is to change its shape and size substantially during flight. Thus, the morphing vehicle is to achieve a broader range of operational modes, all of which will maximize the vehicle performance throughout its mission profile. The dream of human flight has been to mimic birds or insect flights in similar manner since the days of Leonardo da Vinci. Our current aeronautical technology brings us closer to such a feat by vehicle morphing. This is evidenced by the ongoing DARPA contracts on designs of a Sliding-skin concept (in-plane morph) and a Folding wing concept (out-of-plane morph). [1][2][3][4]. However, the R&D of its engineering design/analysis methodology appears to be lagging behind. One such important methodology is the computational capability to assess the flight dynamics and aeroelastic instability, or stability, of a morphing vehicle during the course of its morphing motion.

No abstract

No abstract