Comparison of Constrained Parameterisation Strategies for Aerodynamic Optimisation of Morphing Leading Edge Airfoil

Abstract

In the context of ambitious targets for reducing environmental impact in the aviation sector, dictated by international institutions, morphing aircraft are expected to have potential for achieving the required efficiency increases. However, there are still open issues related to the design and implementation of deformable structures. In this paper, we compare three constrained parameterisation strategies for the aerodynamic design of a morphing leading edge, representing a potential substitute for traditional high-lift systems. In order to facilitate the structural design and promote the feasibility of solutions, we solve a multi-objective optimisation problem, including constraints on axial and bending strain introduced by morphing. A parameterisation method, inherently producing constant arc length curves, is employed in three variants, representing different morphing strategies which provide an increasing level of deformability, by allowing the lower edge of the flexible skin to slide and the gap formed with the fixed spar to be closed by a hatch. The results for the optimisation of a baseline airfoil show that the geometric constraints are effectively handled in the optimisation and the solutions are smooth, with a continuous variation along the Pareto frontier. The larger shape modification allowed by more flexible parameterisation variants enables an increase of the maximum lift coefficient up to 8.35%, and efficiency at 70% of stall incidence up to 4.26%.

Conceptual-level evaluation of a variable stiffness skin for a morphing wing leading edge

“…Figure 3 shows the baseline and target shapes of the leading edge in the current study, where the morphing leading edge accounts for 15% of the chord. The baseline shape resembles the NACA65(3)218 aerofoil, and the target shape is obtained by the multiobjective optimisation of a regional transport aircraft, where the maximum lift coefficient and the lift-to-drag ratio with 70% of the maximum lift coefficient 27 are optimised when the Reynolds number is 9 Â 10 6 and the Mach number is 0.15. The detailed aerodynamic optimisation is not the subject of this paper.…”

“…The detailed aerodynamic optimisation is not the subject of this paper. The current target shape is reconstructed by B splines, and more details of the aerodynamic analysis can be found in Magrini et al 27,28 A similar approach has been applied to optimise the aerofoil of the S4 unmanned aerial system, 29 in which part of the skin was flexible to introduce the shape change of the aerofoil and the aerodynamic optimisation was used to reduce the drag.…”

Multiobjective Optimization for the Aero-Structural Design of Adaptive Compliant Wing Devices

“…Most of the work in the literature on morphing deals with performance optimization [13,14], modeling of morphing wings [15], and design of specific morphing devices [16][17][18]. On the one hand, the issue related to multiple load conditions and conflicting structural requirements needs a dedicated design methodology, and, on the other hand, other open issues are related to the Technology Readiness Level (TRL).…”

Improving aircraft fuel efficiency by using the adaptive wing and winglets

“…The studies of the adaptive wing front edge that uses new composite materials are reported in [30,31]. The aerodyna-mic optimization of the shape of the adaptive wing tip improves the aerodynamic quality of the wing profile by 1.71 %; the authors also note the difficulty of ensuring the predefined wing tip shape using the retractable kinematics [30].…”

“…The aerodyna-mic optimization of the shape of the adaptive wing tip improves the aerodynamic quality of the wing profile by 1.71 %; the authors also note the difficulty of ensuring the predefined wing tip shape using the retractable kinematics [30]. It is shown in [31] that using a seamless adaptive front edge of the wing makes it possible to increase the maximum lift force coefficient to 8.35 % compared to the wing with a deflectable slit tip. Works [32][33][34] examined the aerodynamic characteristics of an adaptive wing and compared them with the original wing with conventional mechanization.…”