Design optimization of a morphing winglet for all flight missions of a civil aircraft

In order to reduce the drag force during various flight missions, airplanes use winglets. In the present work, the DLR-F6 standard wing model is used and the winglet geometry is parameterized to some effective geometrical variables. Correlation coefficients show that, in this standard model, length and cant angle are the most effective variables for modifying the winglet geometry. The flow simulation is carried out using a finite volume computationsl fluid dynamics method using k-ω SST turbulence model. The optimum values of two geometric variables are computed for three flight phases of takeoff, climb and cruise using Genetic Algorithm. By such variations in the winglet geometry, it is shown that up to 70% more drag reduction can be achieved in take-off and climb conditions compared with the reference winglet. While winglet gives the wing beneficial aerodynamic effects, it also has unfavorable structural effects, such as more weight and increased bending moment. Therefore, structural penalty term is added to the objective function to be able to reduce the bending moment while keeping the aerodynamic superiority of the morphing winglet compared to the fixed one. The findings indicate that using a morphing winglet during different flight phases can cut down the fuel consumption of a narrow body civil aircraft up to 820 gallons per day (246,000 gallons annually) in comparison with the initial aircraft (without winglet), which is also 120 gallons per day more than an aircraft with fixed winglet.