Aerostructural Perspective on Winglets

Abstract

This paper presents an aerostructural perspective on the potential benefits of wingletted wings in comparison to planar wings of the same projected span. There is no consensus in the current literature on the e ciency gains possible from winglets. Conclusions made in the past vary significantly depending on the design problem considered and the fidelity of the tools used. The present paper takes a step further towards understanding the tradeo↵s in the design of wingletted wings using high-fidelity numerical optimization based on both purely aerodynamic and fully-coupled aerostructural analysis. The high-fidelity analysis in both cases uses the Euler equations to model the flow along with a friction drag estimate based on the wetted surface area. Three configurations are considered: winglet-up, wingletdown, and planar. The results show that winglets oriented downward produce a greater drag reduction than winglets oriented upward for two reasons. First, the winglet-down configuration moves the tip vortex further away from the wing from a purely aerodynamic standpoint. Second, the winglet-down configuration has a higher projected span at the deflected state due to the structural deflections. This indicates that fully-coupled highfidelity aerostructural optimization is required to quantify the benefits of winglets properly. We present results for two variants of the Boeing 737NG aircraft: B737-600 and B737-900. The winglet-down configuration can reduce the total drag by up to 2% at the same total weight as the optimal planar counterpart. These conclusions are applicable to new wing designs, as opposed to retrofits; the potential e ciency improvements o↵ered by retrofitted winglets may be di↵erent.

Multimodality in Aerodynamic Wing Design Optimization

“…Nonplanar wings have the potential to reduce induced drag beyond what is attainable with a planar wing and an elliptical lift distribution. Previous optimization studies have verified this result [8,31]. We include twist variables in this subproblem because we want to allow the optimizer to converge to an elliptically loaded planar wing if that is the optimal design.…”

Aerostructural Design Exploration of a Wing in Transonic Flow

“…One of the first high-fidelity aerostructural optimizations was conducted by Martins et al [13], who optimized the wing shape and wingbox sizing of a supersonic business jet using Euler computational fluid dynamics (CFD) and a finite-element model. Since then, there have been various other efforts using CFD-based aerostructural optimization with both Euler [14,15] and Reynolds-averaged Navier-Stokes (RANS) models [16][17][18][19][20]. Although more accurate fluid flow models are possible with large-eddy and direct-numerical simulations, the computational cost of such methods renders them prohibitive for wing design optimization with the current technology.…”

“…In airfoil optimization, Buckley et al [40] added a constraint on C l,max into the multipoint objective function to meet safety requirements at a low-speed condition. Rather than constraining C L,max , Khosravi and Zingg [14] included climb drag in the multipoint objective function to encourage improvement in that regime. The whole issue is often skirted by simply imposing limitations on the geometric parametrization to prevent changes that would adversely affect high-lift performance (e.g., minimum leading-edge thickness).…”

Experimental Study and Numerical Simulation of Morphing Characteristics of Bistable Laminates Embedded with 4D Printed Shape Memory Polymers

“…Bistable structures have been widely studied due to its light weight, good mechanical properties, and good space utilization. Therefore, it is widely used in solar tracking [12] , morphing wing [13][14][15][16][17][18] , bionic soft robot [19][20][21] , buffering structure [22] , space deployable structure [23,24] , anti-icing and deicing structure [25] , morphing composite air inlet [26] , origami structure [27][28][29] , energy harvesting [30][31][32][33] and other fields. For the preparation of bistable structures, 3D printing technology was also introduced to improve the designability of the structures [34,35] .…”