Forward Swept Wing Design Study

Abstract

One goal of K2020 is the design of a forward swept wing. In the present work a forward swept wing in cruise configuration is designed. The reference is the K2020 cruise configuration of a backward swept wing which is optimize for minimal drag. To design the forward swept wing an optimization tool and an inverse design tool are used several times. For the optimization the drag is minimized by changing the twist angle of 6 airfoil sections as it is done for the backward swept wing. The application of the inverse design method by Bartelheimer and Takanashi requires that target pressure distributions in several sections are prescribed. The forward swept wing is designed at a target lift coefficient of 0.436. The chord distribution and the span are identical to the backward swept reference wing. The root section of the forward swept wing has to be thinner to avoid strong separations near the fuselage. The front part of the fuselage of the forward swept wing configuration has been extended. Even if the flow on the fuselage surface is computed inviscid an influence on the aerodynamic performance of the extension of the fuselage is verified. Because of a reduction of the sweep angle during this study the optimized forward swept wing can finally be installed on a fuselage having a length of the backward swept reference aircraft. Using the forward swept model the lift to drag ratio of the optimized backward swept reference model cannot be reached completely. This is caused by the fuselage wing junction which is equipped with a belly fairing which is designed for a backward swept wing and is not adapted for a forward swept wing. Regarding the performance of the wing only, the forward swept wing shows even better results than the backward swept wing.