Abstract:

ESDU 01007 gives factors for the determination of the theoretical trailing vortex drag of straight-tapered or cranked wings, with or without camber and twist and with part-span trailing-edge plain flaps. The factors have been derived from the spanwise loading distributions generated by Multhopp-Richardson lifting-surface solutions, with some adjustment via two correction factors. The primary correction factor was derived to give agreement with the theoretical results of ESDU 74035 for plane wings; there the underlying spanwise loading came from a different lifting-surface solution with additional spanwise stations incorporated between the collocation stations to improve the accuracy of the downwash integration and so provide more reliable values of the vortex drag factor. A modification of the primary correction factor for application to wings with part-span flaps was derived from comparisons with an in-house vortex lattice model over a wide range of configurations. Data for plain flaps with a flap chord ratio of 0.3 are tabulated for 115 planforms and 47 flap span conditions. Selective graphical presentations are given to illustrate the variation of the drag factors with wing and flap geometry. A Fortran ESDUpac program, A0107, provides data for the general case. Guidance is given on the application of the method to flaps other than plain, and with possible chord extension, through the adoption of an effective plain flap chord that is chosen so that the centre of incremental lift due to flap deflection matches that of the actual flap. Limitations on the use of the program are fully documented. Worked examples demonstrate the use of the tabulated data and of the ESDUpac. One example includes the treatment of vortex drag as part of the total lift-dependent drag in the analysis of experimental data.