Aeroelastic Modelling of Highly Flexible Wings

Abstract

This paper details five aeroelastic modelling methods applied to the study of an example high aspect ratio wing subject to high loads resulting in large structural deformations. Each method is discussed in turn and example static results from each are compared. Overall agreement is illustrated between the methods for key quantities of interest although aerodynamic modelling choices regarding the orientation of aero forces is observed to play a significant role in the agreement between predicted distributed loads and deflections. Quantitative differences resulting from linearisation of the wing model are also presented and discussed. It is found that by linearising the problem, wing deflection, aerodynamic forces and root bending are all over-estimated. Large differences are also observed between linear and nonlinear predictions of root twist, however the modelling of drag effects is deemed important to the exact nature of the observed discrepancy. Altogether, linearised assumptions are shown to have a noticeable impact on the accuracy of predicted results for the considered wing test case and are deemed unsuitable in isolation for the analysis of this class of flexible problem.

Effects of Geometric Nonlinearities on the Fidelity of Aeroelasticity Loads Analyses of Very Flexible Airframes

“…When the modified iterative method presented in this section is compared to the method implemented in [9], it can be seen that the inclusion of the wing twist into the iterative procedure brings it much closer to a linear flexible aeroelasticity analysis for a stiff 92 airframe. The variation of local angle of attack along the wingspan is shown in Figure 18, and the results for out of plane bending, out of plane shear, and wing torsional loads along the wing span are presented in Figure 19, Figure 20, and Figure 21.…”

“…As such, the effects of geometric nonlinearities have to be considered during the loads "loop" process especially in the aeroelastic analysis of aircraft, to obtain higher fidelity loads and better model its response under large deformations. Therefore, the effects of geometric nonlinearity needs to be included in any high fidelity aeroelastic solution sequence [9].…”

“…In the first half of the thesis, a geometrically static aeroelastic solution method is presented, significantly improving upon the fidelity of loads compared to the work presented in literature [9]. The major advantage of the work presented over existing nonlinear aeroelastic solvers is the accessibility to engineers working in the aerospace industry.…”

“…The difference in the loads between the nonlinear methodologies are significant as the out of plane loads calculated by the modified nonlinear methodology are lower than the unmodified loop. This is a result of the change in angle of attack along the outer edges of the wingspan, as shown in Figure 18, which is not considered in the original iterative method [9]. As such, the rest of the results will be presented using the modified nonlinear methodology which includes twist effects.…”

“…The effects of geometrical nonlinearities on the aeroelastic loads of aircraft in static flight conditions has been studied quite thoroughly by several authors [9], [59], [77], [78].…”