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Proceedings ArticleDOI

Reduction of Induced Drag in Con guration Flight using Wing Twist at Post-Stall Angles of Attack

About: The article was published on 2016-01-04. It has received None citations till now. The article focuses on the topics: Wing twist & Lift-induced drag.
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Book ChapterDOI
01 Jan 1989
TL;DR: In this article, an inviscid linear-vorticity panel method with a Karman-Tsien compressiblity correction is developed for direct and mixed-inverse modes.
Abstract: Calculation procedures for viscous/inviscid analysis and mixed-inverse design of subcritical airfoils are presented. An inviscid linear-vorticity panel method with a Karman-Tsien compressiblity correction is developed for direct and mixed-inverse modes. Source distributions superimposed on the airfoil and wake permit modeling of viscous layer influence on the potential flow. A two-equation lagged dissipation integral method is used to represent the viscous layers. Both laminar and turbulent layers are treated, with an e 9-type amplification formulation determinining the transition point. The boundary layer and transition equations are solved simultaneously with the inviscid flowfield by a global Newton method. The procedure is especially suitable for rapid analysis of low Reynolds number airfoil flows with transitional separation bubbles. Surface pressure distributions and entire polars are calculated and compared with experimental data. Design procedure examples are also presented.

2,185 citations

Journal ArticleDOI
TL;DR: In this article, a more practical form of the analytical solution for the effects of geometric and aerodynamic twist (washout) on the low-Mach-number performance of a finite wing of arbitrary planform is presented.
Abstract: A more practical form of the analytical solution for the effects of geometric and aerodynamic twist (washout) on the low-Mach-number performance of a finite wing of arbitrary planform is presented. This infinite series solution is based on Prandtl's classical lifting-line theory and the Fourier coefficients are presented in a form that only depends on wing geometry

108 citations

Journal ArticleDOI
TL;DR: In this paper, the results of wind-tunnel tests conducted to evaluate aerodynamics characteristics of aircraft in formation flight were reported, which revealed that the spatial offset and the angle of attack of the leading wing had significant impact on the trailing aircraft.
Abstract: Reported are the results of wind-tunnel tests conducted to evaluate aerodynamics characteristics of aircraft in formation flight. A vortex-lattice numerical scheme was used to investigate the effect of spatial offset (horizontal and vertical) between the leading and trailing wings. The wind-tunnel test configurations consisted of echelon, chevron, and in-line formations. Analysis of the data revealed that the spatial offset and the angle of attack of the leading wing had significant impact on the trailing aircraft. For some test conditions an increase in lift-to-drag ratio of the trailing aircraft was measured. Variation in C Lmax and/or α stall was observed as well. At higher angles of attack of the leading wing, the C L-α curve of the trailing aircraft was significantly altered.

73 citations

Journal ArticleDOI
TL;DR: In this article, a novel scheme is presented for an iterative decambering approach to predict the post-stall characteristics of wings using known section data as inputs, which differs from earlier ones in the details of how the residual is computed.
Abstract: A novel scheme is presented for an iterative decambering approach to predict the post-stall characteristics of wings using known section data as inputs. The new scheme differs from earlier ones in the details of how the residual is computed. With this scheme, multiple solutions at high angles of attack are brought to light right during the computation of the residual for the Newton iteration. As with earlier schemes, multiple solutions are obtained for wings at high angles of attack and the resulting converged solution depends on the initial conditions used for the iteration. In general, the new scheme is found to be more robust at achieving convergence. Results are presented for a rectangular wing with two different airfoil lift curves and for a wing-tail configuration.

65 citations

Proceedings ArticleDOI
04 Jan 2010
TL;DR: In this paper, a method for achieving an arbitrary lift distribution with an arbitrary planform is presented through optimizing aerodynamic twist for a given number of either known airfoils or airframes to be designed.
Abstract: A method for achieving an arbitrary lift distribution with an arbitrary planform is presented. This is accomplished through optimizing aerodynamic twist for a given number of either known airfoils or airfoils to be designed. The spanwise locations of these airfoils are optimized to get as close to the desired lift distribution as possible. Airfoils are linearly interpolated between these points. After aerodynamic twist, the planform is twisted geometrically using radial basis functions to model the twist distribution. The aerodynamic influence of each twist distribution is determined and all are superimposed to determine the function weights of each twist function, yielding the optimal twist to match the given lift. This method has been shown to match both an elliptical and a triangular lift distribution for an arbitrary planform. This method can also be used with any fidelity model, creating a powerful design tool.

14 citations