An Iterative Decambering Approach for Post-Stall Prediction of Wing Characteristics from Known Section Data
06 Jan 2003-
About: The article was published on 2003-01-06. It has received 10 citations till now. The article focuses on the topics: Decambering & Post stall.
Citations
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TL;DR: In this paper, a thorough analysis on the circulation-based and angle-of-attack-based correction methods (Γ and α) highlights their respective numerical poststall characteristics, and a strongly coupled algorithm is presented, allowing to bypass the interpolation phase via the use of Legendre polynomials.
Abstract: Numerical algorithms and solutions of generalized nonlinear lifting-line theory over an elliptical wing are examined, with emphasis on near/poststall flows. First, a thorough analysis on the circulation-based and angle-of-attack-based correction methods (Γ and α methods, respectively) highlights their respective numerical poststall characteristics. The stability of the method is demonstrated, producing single and multiple solutions in the pre- and poststall regions, respectively. Second, artificial dissipation added to the α method is shown to be an effective means of controlling the poststall flow region. Finally, a strongly coupled algorithm is presented, allowing to bypass the interpolation phase via the use of Legendre polynomials. The model sheds light on poststall flow behavior, in agreement with several papers studying formation of stall cell patterns.
46 citations
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TL;DR: In this paper, a nonlinear lifting-line-theory algorithm for the prediction of aerodynamic coefficients and lifting-surface-pressure distribution for multiple aircraft configurations is presented, which is applied to isolated wing, high-lift systems (slat/main/flap), and multisurface configurations.
Abstract: A modern nonlinear-lifting-line-theory algorithm allowing the prediction of aerodynamic coefficients and lifting-surface-pressure distribution for multiple aircraft configurations is presented. The algorithm is applied to isolated wing, high-lift systems (slat/main/flap), and multisurface configurations, with emphasis on the treatment of high-lift geometry representations. The fuselage is not geometrically modeled, but its influence is appropriately taken into account for the aerodynamic-coefficient evaluation. The results show good agreements with wind-tunnel and/or high-fidelity numerical data for the prediction of the maximum lift coefficient and the poststall behavior in subsonic and transonic conditions. The use of sectional airfoil data obtained via solutions of the Reynolds-averaged Navier–Stokes equations with infinite-swept-wing assumptions—so-called 2.5-dimensional model—is shown to greatly improve the results over traditional two-dimensional solutions.
35 citations
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TL;DR: In this paper, the authors describe the development and testing of a variable-span wing (VSW) concept, which uses a viscous two-dimensional panel method formulation coupled with an aerodynamic shape optimisation code.
Abstract: This paper describes the development and testing of a variable-span wing (VSW) concept. An aerodynamic shape optimisation code, which uses a viscous two-dimensional panel method formulation coupled...
20 citations
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TL;DR: In this article, a two-pronged approach is presented to tailor an airfoil for an aircraft: 1) an approach in which aircraft performance simulations are used to study the effects of aerodynamic changes, and 2) an analytical approach to determine expressions that provide guidance in sizing and locating the low-drag range.
Abstract: Even with all of the advances in airfoil and aircraft design, there remains little guidance on how to tailor an airfoil to suit a particular aircraft. A two-pronged approach is presented to tailor an airfoil for an aircraft: 1) an approach in which aircraft performance simulations are used to study the effects of airfoil changes and to guide the airfoil design and 2) an analytical approach to determine expressions that provide guidance in sizing and locating the airfoil low-drag range. The analytical study shows that there is an ideal value for the lift coefficient for the lower corner of the airfoil low-drag range when the airfoil is tailored for aircraft level-flight maximum speed. Likewise, there is an ideal value for the lift coefficient for the upper corner of the low-drag range when the airfoil is tailored for maximizing the aircraft range. These ideal locations are functions of the amount of laminar flow on the upper and lower surfaces of the airfoil and also depend on the geometry, drag, and power characteristics of the aircraft. Comparison of the results from the two approaches for a hypothetical general aviation aircraft are presented to validate the expressions derived in the analytical approach
17 citations
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TL;DR: In this paper, a viscous lifting line method for three-dimensional supercavitating hydrofoils is presented, which is designed to allow for the strong nonlinear hydrodynamic characteristic of two-dimensio...
Abstract: A new viscous lifting-line method for three-dimensional supercavitating hydrofoils is presented. The method is designed to allow for the strong nonlinear hydrodynamic characteristic of two-dimensio...
13 citations
References
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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
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TL;DR: Several recent developments in airfoil and wing theory have as their goals the extension of classical methods to account for characteristically viscous phenomena such as separation and stalling as discussed by the authors.
Abstract: Several recent developments in airfoil and wing theory have as thjeir goals the extension of classical methods to account for characteristically viscous phenomena. Airfoil theory has always recognized the existence of such phenomena as explanations of the presence of circulation and vortex wakes; these new investigations are attempts to include detailed descriptions in theoretical models or to extend classical models into areas of strong viscous effects, such as separation and stalling. Some of these studies follow directly from suggestions made by von Karman, and others are reminiscent of his earlier research. This review is concerned with investigations in four categories: (1) the theory of profiles with boundary layers in steady flow, (2) the theory of profiles with boundary layers in unsteady flow, including extensions of unsteady airfoil theory, (3) the theory of wings with leading-edge separation, and (4) Prandtl wing theory applied to partially stalled wings.
171 citations
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TL;DR: In this paper, a numerical iterative solution to the classical Prandtl lifting-line theory, suitably modified for poststall behavior, is used to study the aerodynamic characteristics of straight rectangular finite wings with and without leading-edge droop.
Abstract: A numerical iterative solution to the classical Prandtl lifting-line theory, suitably modified for poststall behavior, is used to study the aerodynamic characteristics of straight rectangular finite wings with and without leading-edge droop. This study is prompted by the use of such leading-edge modifications to inhibit stall/spins in light general aviation aircraft. The results indicate that lifting-line solutions at high angle of attack can be obtained that agree with experimental data to within 20%, and much closer for many cases. Therefore, such solutions give reasonable preliminary engineering results for both drooped and undrooped wings in the poststall region. However, as predicted by von Karman, the lifting-line solutions are not unique when sectional negative lift slopes are encountered. In addition, the present numerical results always yield symmetrical lift distributions along the span, in contrast to the asymmetrical solutions observed by Schairer in the late 1930's. Finally, a series of parametric tests at low angle of attack indicate that the effect of drooped leading edges on aircraft cruise performance is minimal.
111 citations
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TL;DR: In this article, a high-lift system design methodology that can be incorporated during the early stages of aircraft development is presented and thus has the potential to provide a superior and more cost-effective vehicle than one developed utilizing traditional linear design methods.
Abstract: A high-lift system design methodology that can be incorporated during the early stages of aircraft development is presented and thus has the potential to provide a superior and more cost-effective vehicle than one developed utilizing traditional linear design methods. The present methodology offers two different levels of e delity: one applicable to the conceptual design stage and the other to the preliminary design stage. The underlying e ow solver couples a three-dimensional nonlinear Weissinger method with two-dimensional viscous data to provide fast and accurate aerodynamic predictions for high-lift cone gurations. Several test cases that illustrate the capabilities of this hybrid e ow solver are presented.
64 citations
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15 Jun 1976
TL;DR: In this article, a computational procedure is developed for predicting the time dependent longitudinal and lateral aerodynamic characteristics of wing-body configurations at angles of attack up to and beyond stall, based on nonlinear lifting line theory which has been modified to include unsteady wake effects.
Abstract: : A computational procedure has been developed for predicting the time dependent longitudinal and lateral aerodynamic characteristics of wing-body configurations at angles of attack up to and beyond stall. The purpose of the procedure is to provide the aircraft designer with a tool for simulating and alleviating such adverse wing stalling characteristics as wing rock, wing drop, loss of roll control or roll control reversal, etc. and thereby lead to the design of aircraft with improved stall, departure and spin resistance characteristics. The procedure is based on nonlinear lifting line theory which has been modified to include unsteady wake effects.
45 citations
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