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Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2007. / Engineers and Technologists have found several approaches to control the shape of an aerofoil and improve the performance of a wing at different flow regimes; this research has been done at 2D level. In this work, a novel approach has been developed. The inspiration for this work comes from biological research. A 3D wing body has been modeled and flow conditions around it were simulated by advanced computer technology. The fabrication of the wing, based on the design optimization model, has been conducted using rapid prototyping technology. The unique thermal and mechanical properties that are exhibited by shape memory alloys (SMAs) have presented an exciting design possibility in the field of aerospace engineering. This kind of smart material was incorporated in the wing structure and when activated can alter the shape of the wing, thus effectively increasing the efficiency of a wing in flight, at several different flow regimes.

Extensive hot-wire measurements were conducted in an incompressible turbulent flow around a wing-body junction. The measurements were performed adjacent to the body and up to 11.56 chord lengths downstream of the body. The junction wake flow entered an adverse pressure gradient region approximately 6 chord lengths downstream. This region's geometry approximated the aft portion of an aircraft fuselage or a submersible's hull. The body geometry was formed by joining a 3:2 elliptic nose to a NACA 0020 tail section at their respective maximum thickness locations. The author's measurements were taken with approach flow conditions of Reθ = 6,300, and δ/T = .513, where T is the maximum body thickness. The results clearly show the characteristic horseshoe vortex flow structure. The vortex flow structure is elliptically shaped, with â (W)/â Y forming the primary component of streamwise vorticity. Near wall measurements show a thin layer of highly concentrated vorticity, underneath and opposite in sign to the primary vortex, which is created by the wall no-slip condition. The development of the flow distortions and associated vorticity distributions are highly dependent on the geometry-induced pressure gradients and resulting flow skewing directions. A quantity known as the "distortion function" was used to separate the distortive effects of the secondary flow from those of the body and the local "2-D" boundary layer. The distortion function revealed that the adverse pressure gradient flow distortions grew primarily because of the increasing boundary layer thickness. The author's results were compared to several other data sets obtained using the same body shape, enabling the determination of the approach boundary layer effects. The primary secondary flow structure was found to scale on T in the vertical and cross-stream directions, revealing that the juncture flow is driven by the appendage geometry and associated pressure gradients. A parameter known as the momentum deficit factor (MDF = (ReÏ ) 2 (θ/T) was found to correlate the observed trends in mean flow distortion magnitudes and vorticity distribution. Variations in flow skewing were observed to be comparable to changes in MDF, suggesting that this flow parameter changes the effective skewing magnitudes around a wing-body junction. Mean flow distortions were found to increase with decreasing values of MDF. A numerical study was also performed to gain additional insights into the effects of appendage nose geometry. The velocity distributions around approximately 30 different appendage cross-sections were estimated using 2-D potential flow calculations. A correlation was found between the appendage nose bluntness and the average vortex stretching rate, and also between the invisicid velocity distribution and an experimentally determined non-dimensional circulation estimate. / Master of Science

The paraglider wing consists of leading-edge booms and a keel boom joined together at the nose and a flexible sail whose surface carries the aerodynamic pressure loading. The payload is suspended beneath the wing by cables which are used to control the wing. Adjusting the length of these cables controls the glide path of the wing by shifting the position of the payload with respect to the wing. The deflected shape of the sail depends on the pressure distribution over the sail; the pressure distribution in turn depends aerodynamically on the deflected shape of the sail. It is the purpose of this thesis to derive the equilibrium equations for the sail and to integrate these equations to find expressions for the stress resultants in terms of the pressure on the sail and the deflected shape of the sail. By integration of these expressions for stress resultants, along the edges of the sail, the resultant forces applied by the sail to the leading-edge booms and keel boom are found. Then, by considering the streamwise components and the components normal to the stream of the boom forces, the drag and lift forces are obtained. These expressions for the lift and drag forces, and for the boom forces, are given in terms of the boundary value of the stress resultants and can be applied for any aerodynamic theory appropriate to the speed range being considered. When the appropriate aerodynamic relationship, between pressure and deflected shape, is substituted into the boundary, conditions for stress resultant at the trailing edge of the sai1, the criterion for determining the deflected shape is obtained. Once the deflected shape is known all the other quantities can be determined. In order to show an application of the analysis, the equations were specialized for Newtonian impact theory. This theory yields a simple pressure-deflected relationship. This aerodynamic theory, which has found applications for hypersonic speeds, has been employed since it shows the application of the method in a simple manner. In addition, it has been previously for a rigid idealization of a paraglider wing and thus provides a ready means for comparison. Hence numerical results can be used to test the accuracy of the rigid idealization. These results showed that the deflected shape of the flexible paraglider wing differed considerable from the conical shape of the rigid wing over the complete range of angle of attack. The differences in shape result in different pressure distributions over the surface of the wing and as a result the lift and drag coefficients, and especially the lift-to-drag ratio, for the flexible wing were significantly different from the values for the rigid wing. The boom forces and the distribution of stress resultants over the surface of the sail were obtained. The stress resultants along radial lines were found to be proportional to the distance from the nose of the wing. The calculated stress resultants and boom forces provide a basis for design of sails, booms, shroud lines, and spreader bars for a paraglider for hypersonic flight. Effects of dihedral angle (raising or lowering of the leading-edge booms relative to the keel) were also considered. The pressure distributions, the lift and drag coefficients, and the ratio to drag were found for several dihedral angles at a given angle of attack. / Ph. D.

The research contributes toward a fully integrated multidisciplinary wing design synthesis by development of an appropriate structural model. The goal is to bridge the gap between highly idealized structural beam / aerodynamic strip models and the very detailed finite element and computational fluid dynamics, FEM/CFD, techniques. The former provides insufficient accuracy for flutter analysis of modern low aspect ratio composite wings. The latter is too computationally intensive for use in the inner loop of a simultaneous multidisciplinary optimization problem. The derived model provides a useful preliminary design tool as well. / Ph. D.

A theory and method have been developed and design change drawn, for the estimation of certain stability derivatives for wings of arbitrary platform in subsonic flow. / Ph. D.

Wing structures often contain nonlinearities which affect their aeroelastic behavior and performance characteristics. Aerodynamic flows at transonic Mach numbers generate nonlinear aerodynamic forces on the wing affecting the aeroelastic response of the wing. Analysis techniques accounting for these structural and aerodynamic nonlinearities, and an understanding of their potential influence on the flutter mechanism of two-dimensional and three-dimensional wing-structures model are the main objective of this study. Two different categories of structural nonlinearities, i.e. (i) distributed nonlinearity and (ii) concentrated nonlinearity , are considered. The concentrated nonlinearities are mathematically modeled using Asymptotic Expansion method which based on on the Krylov-Bogoliubov-Mitropolski technique. The effective stiffness coefficient of a nonlinear element is defined as the ratio of the amplitude of the Fourier series expansion of the load and the amplitude of the displacement of that element. The effects of distributed nonlinearities on the aeroelastic characteristic of three-dimensional wing model are also investigated. The influences of this type of nonlinearity is treated in a quasi-nonlinear approach, which allows the variation of the the natural frequencies and damping factor of the structure model with respect to the amplitude of the motion. The transonic aerodynamic pressure distributions have been obtained by solving the unsteady Transonic Small Disturbance ( TSD ) flow equation using finite-difference techniques. An Alternating Direction Implicit ( ADI ) algorithm was used for two-dimensional flow model, and an Approximate Factorization ( AF ) algorithm was used for three-dimensional flow model. The finite-state generalized aerodynamic forces used in the aeroelastic analysis have been calculated by employing the Method of Harmonic Oscillation and the Pulse Transfer Function analysis. The solution of the aeroelastic equation in frequency domain is obtained by representing the equation in a finite-state form through the modal approach using Lagrange’s equation. The flutter boundary is obtained by solving this equation using the classical U-g method and root locus analysis. Flutter analysis of a two degree-of-freedom , two-dimensional typical wing sections with nonlinear torsional springs are studied. The aeroelastic responses of the system are obtained by integrating the nonlinear structural terms and aerodynamic terms simultaneously using Newmark-β and Wilson-θ methods. Flutter results obtained from both time integration and eigenvalue solutions are compared. These two results, in general, are in agreement. Flutter behavior of a simple three-dimensional swept wing model is also investigated. Comparison of the flutter boundary obtained by using the eigenvalue solution with flutter data from wind-tunnel experiments are made. / Ph. D.

no abstract provided by author / Master of Science