DRAGDUE TOLIFT: Concepts for Prediction and Reduction

Abstract

▪ Abstract This article describes some of the fundamental ideas underlying methods for induced-drag prediction and reduction. A review of current analysis and design methods, including their development and common approximations, is followed by a survey of several approaches to lift-dependent drag reduction. Recent concepts for wing planform optimization, highly nonplanar surfaces, and various tip devices may lead to incremental but important gains in aircraft performance. Focusing on relatively high-aspect-ratio subsonic wings, the review suggests that opportunities for new concepts remain, but the greatest challenge lies in their integration with other aspects of the system.

Power Balance in Aerodynamic Flows

“…The early work of Betz [1], Jones [2] and Oswatisch [3] focused on drag, while Maskell [4] considered both lift and drag for incompressible flow, and Kroo [5] reviewed various techniques for induced drag prediction and reduction. The recent efforts of VanDam [6], Giles and Cummings [7], and Kusunose [8] have treated the general compressible case, also with enthalpy addition from engines.…”

Wake-Model Effects on Induced Drag Prediction of Staggered Boxwings

“…Their total aerodynamic performance must be evaluated as a trade-off between induced drag and contributions of other drag sources. For example, viscous drag penalties, associated with the increased wetted area, diminish the advantage of induced drag savings [1,19]. For highly non-planar configurations, potential-flow induced drag predictions can have limited accuracy.…”

“…The impact on aircraft performance is profound. For a commercial aircraft, induced drag accounts for approximately 40% of the total drag during cruise flight and up to 90% during takeoff [1]. A marginal reduction in induced drag translates into considerable savings in fuel and emissions or facilitates a range extension.…”

“…A marginal reduction in induced drag translates into considerable savings in fuel and emissions or facilitates a range extension. Considering indirect effects associated with an improved climb performance and a higher maximum takeoff mass, gains easily multiply [1]. Against the background of the objectives set in Flightpath 2050 [2], measures that provide lower induced drag support the efforts to attain a cutback in fuel consumption and climate reactive emissions.…”

“…The inviscid aerodynamic advantage of these configurations can primarily be related to the bound circulation being distributed over a larger effective wingspan. This lowers the spanwise loading and reduces the average downwash velocity of the system compared to that of an optimally-loaded planar wing of equivalent span and lift [1]. Based on linear potential-flow theory, the boxwing achieves the highest span efficiency or lowest induced drag for a given projected wingspan and lift [7,[13][14][15][16][17][18]].…”