The Impacts of Aspect Ratio Variations in Preliminary Design of a Mid-Range Jet Transport Aircraft

Kurzfassung

Reducing drag is an essential challenge in aeronautics. The lower the drag, the better the fuel efficiency of the aircraft. Indeed, the thrust generated by the engines is the force that balances the drag and it can be reduced by reducing the drag. The aircraft drag comes from the fuselage, wing, tail and engine; however, the largest part of the drag comes from the wing. The total drag of the wing is the sum of the profile drag, composed on frictional and pressure drag, and the induced drag. The frictional drag is related to the surface area exposed to the flow and the pressure drag is related to the cross sectional area of the body. The induced drag represents a large part of the total wing drag and can be reduced in two different ways: increasing the Oswald factor, which means get as close as possible to an elliptical lift distribution, or increasing the wing's aspect ratio, which is the ratio between the square of the span and the surface of the wing. In this work, the second option is chosen and the studied aircraft is a mid-range jet transport aircraft concept developed by the German Aerospace Center (DLR) which has an aspect ratio of 15.6. Three methods of aspect ratio increase are developed and the results obtained by each method are analysed and compared. cpacs-MONA, the computational framework developed by DLR, is used to generate the structural and aerodynamic finite element models and to evaluate the aerodynamic, structural and aeroelastic characteristics of the aircraft. Particular methods to check the reliability of the results are used and a method based on a Fourier series decomposition is implemented to compute the Oswald factor and to evaluate the induced drag more accurately.