scholarly journals Numerical Computation of Subsonic Oscillatory Airforce Coefficients for Wing-Winglet Configurations

2007 ◽  
Vol 1 (3) ◽  
pp. 303-328
Author(s):  
C.W. Cheung
Keyword(s):  
Computer Program ◽  
Theoretical Development ◽  
Dihedral Angles ◽  
Aircraft Wing ◽  
Lattice Method ◽  
Surface Theory ◽  
Transport Aircraft ◽  
Harmonic Motion ◽  
Doublet Lattice Method ◽  
Stiffness And Damping

This paper presents the theoretical development and numerical results of a lifting-surface theory for calculating oscillating airforce coefficients for wing-winglet configurations and it follows the author's previous paper on the extension of Davies' T-tail theory for cruciform-tail configurations. The wing-winglet configurations are assumed to vibrate in a simple harmonic motion of infinitesimal amplitude in a subsonic airstream such that linearised aerodynamic theory is applicable for the analysis of the motion. The modes of displacement of the wing-winglet configuration may be either symmetric or antisysmmetric with respect to the centre-line of the configuration in the direction of the flow. A computer program has been developed for the evaluation of oscillatory airforce coefficients for wing-winglet configurations. Aerodynamic stiffness and damping matrices which are normally used for aeroelastic calculations have been obtained for a typical transport aircraft wing-winglet configuration at two winglet dihedral angles and comparisons have been made against those calculated by an alternative doublet-lattice method. The comparisons have been shown to be satisfactory.

scholarly journals Enumeration and investigation of acute 0/1-simplices modulo the action of the hyperoctahedral group

2017 ◽  
Vol 5 (1) ◽  
pp. 158-201
Author(s):  
Jan Brandts ◽  
Apo Cihangir
Keyword(s):  
Convex Hull ◽  
Computer Program ◽  
Explicit Form ◽  
Linear Algebra ◽  
Dihedral Angles ◽  
Cycle Index ◽  
Hyperoctahedral Group ◽  
Diagonally Dominant ◽  
Group B ◽  
Cycle Indices

Abstract The convex hull of n + 1 affinely independent vertices of the unit n-cube In is called a 0/1-simplex. It is nonobtuse if none its dihedral angles is obtuse, and acute if additionally none of them is right. In terms of linear algebra, acute 0/1-simplices in In can be described by nonsingular 0/1-matrices P of size n × n whose Gramians G = PTP have an inverse that is strictly diagonally dominant, with negative off-diagonal entries [6, 7]. The first part of this paper deals with giving a detailed description of how to efficiently compute, by means of a computer program, a representative from each orbit of an acute 0/1-simplex under the action of the hyperoctahedral group Bn [17] of symmetries of In. A side product of the investigations is a simple code that computes the cycle index of Bn, which can in explicit form only be found in the literature [11] for n ≤ 6. Using the computed cycle indices for B3, . . . ,B11 in combination with Pólya’s theory of enumeration shows that acute 0/1-simplices are extremely rare among all 0/1-simplices. In the second part of the paper, we study the 0/1-matrices that represent the acute 0/1-simplices that were generated by our code from a mathematical perspective. One of the patterns observed in the data involves unreduced upper Hessenberg 0/1-matrices of size n × n, block-partitioned according to certain integer compositions of n. These patterns will be fully explained using a so-called One Neighbor Theorem [4]. Additionally, we are able to prove that the volumes of the corresponding acute simplices are in one-to-one correspondence with the part of Kepler’s Tree of Fractions [1, 24] that enumerates ℚ ⋂ (0, 1). Another key ingredient in the proofs is the fact that the Gramians of the unreduced upper Hessenberg matrices involved are strictly ultrametric [14, 26] matrices.

Further Refinement of the Subsonic Doublet-Lattice Method

1998 ◽  
Vol 35 (5) ◽  
pp. 720-727 ◽  
Author(s):  
William P. Rodden ◽  
Paul F. Taylor ◽  
Samuel C. McIntosh
Keyword(s):  
Lattice Method ◽  
Doublet Lattice Method

Structural sizing for the weight estimation of a very light aircraft wing

2018 ◽  
Vol 232 (14) ◽  
pp. 2681-2687
Author(s):  
Abdelkader Benaouali ◽  
Robert Rogólski ◽  
Stanisław Kachel
Keyword(s):  
Finite Element ◽  
Design Process ◽  
Geometric Modeling ◽  
Optimization Techniques ◽  
Product Development Process ◽  
Optimization Strategy ◽  
Aircraft Wing ◽  
Lattice Method ◽  
Vortex Lattice Method

The design process is no longer a trial-and-error procedure due to the introduction of computer-aided tools and optimization techniques. The product development process is therefore accelerated, allowing to produce more in a relatively lesser time. Moreover, the best possible design, with regard to the performance, can hence be obtained. When applied to the design of an aircraft wing, the optimization objective is usually to minimize the structural weight under failure-based constraints. This paper presents an optimization strategy that allows the determination of the wing surface structural thicknesses corresponding to the minimal weight while keeping the structure safe in terms of strength and buckling. This strategy is applied for the wing sizing process of a new two-seater very light aircraft, currently under development. The design process goes through geometric modeling, aerodynamic calculations using vortex lattice method, and finite element modeling. Structural optimization is performed within MATLAB, and is based on the automatic execution of the finite element solver MSC.NASTRAN.

An Analytic and Experimental Investigation of the Aerodynamic Performance Enhancements of Multiple Winglet Configurations

2005 ◽  
Author(s):  
D. S. Miklosovic ◽  
P. M. Bookey
Keyword(s):  
Aspect Ratio ◽  
Vortex Lattice ◽  
Dihedral Angles ◽  
Pitching Moment ◽  
Lattice Method ◽  
Vortex Lattice Method ◽  
Moment Coefficient ◽  
Effectiveness And Efficiency ◽  
Low Speed Wind Tunnel ◽  
Experimental Effort

An experimental effort was undertaken to assess the effectiveness and efficiency of three winglets mounted chordwise to the tip of a rectangular wing (NACA 0018 section). The winglets, with an aspect ratio of 3.6, were mounted on a half-span wing having an aspect ratio of 3.1. Twenty configurations of varying dihedral arrangements were analyzed with a vortex lattice method and tested in a low-speed wind tunnel at a Reynolds number of 600,000. In general, the arrangements involving high dihedral angles had lower performance increments, due to lower lift and higher interference drag. More specifically, the results showed that the winglets placed at 60, 45, and 30 degrees, respectively, produced nominal 4% higher lift and 46% lower drag. The most dramatic findings from this study show that positioning the winglet dihedral angles had the result of adjusting the point of maximum L/D and the magnitude of the pitching moment coefficient. These observations suggest that multiple winglet dihedral changes affect the lift, drag, and pitching moment in such a way that they are feasible for use as actively-controlled surfaces to improve the performance of aircraft at various flight conditions and to “tune” the longitudinal stability characteristics of the wing.

Conceptual Design Optimization With Economic Uncertainty: An Application to Interactions Between Designers and Airlines

2014 ◽  
Author(s):  
Garrett Waycaster ◽  
Christian Bes ◽  
Volodymyr Bilotkach ◽  
Christian Gogu ◽  
Raphael Haftka ◽  
...  
Keyword(s):  
Asymmetric Information ◽  
Design Optimization ◽  
Operating Costs ◽  
Economic Uncertainty ◽  
Aircraft Wing ◽  
Design Decisions ◽  
Transport Aircraft ◽  
Sources Of Uncertainty ◽  
Optimal Decisions ◽  
Engineering Problems

Many engineering problems involve interactions between multiple decisions makers, or stakeholders, each with their own objectives and uncertainties. Considering these interactions during design optimization allows us to account for new sources of uncertainty, which we refer to as economic uncertainty. In this paper, we consider an application of optimization considering interactions between aircraft designers and airlines based on the design of a commercial transport aircraft wing. We consider that the aircraft designer makes their design decisions first, and therefore must predict the reaction of the airline. We focus on the effect of two economic uncertainties: uncertainty that would normally only affect the airline and uncertainty due to asymmetric information, or errors in the designers’ understanding of the airlines’ preferences. We find that these uncertainties play a significant role in the optimal decisions by both airlines and designers. We also show that asymmetric information may actually be beneficial for both stakeholders in certain cases, where both players benefit from the aircraft designer underestimating the operating costs of the airline.

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