Abstract: The joined-wing configuration, as compared with the normal configuration, is characterized by low structural weight, small induced drag, big lift coefficient and good stability. Starting from the lifting line theory and introducing Prandtl assumption of interference factor, this article derives an aerodynamic solution model for parallel joined-wing layout, and provides the value range of its interference factor. This model retains the advantages of engineering estimation in simplicity and rapidity, and a comparison with the calculation results of computational fluid dynamics (CFD) indicates that the precision of this model is preferable. The results show that an increase of aspect ratio, span ratio and space of the front wing, while keeping the wing area invariable, could reduce the total induced drag effectively. The induced drag is reduced by 28% as compared with the single-wing configuration.

Key words: joined-wing, aerodynamics model, interference factor, engineering estimation, computational fluid dynamics