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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

An investigation to determine the low-speed lateral-directional characteristics of a generic 74-degree delta wing-body configuration employing the latest generation, gothic planform vortex flaps has been conducted. In addition, the theoretical estimates from VORSTAB were compared against experimental data to aid in documenting this new method. VORSTAB is an extension of the Quasi-Vortex-Lattice Method of Lan which empirically accounts for vortex breakdown effects in the calculation of longitudinal and lateral-directional aerodynamic characteristics. The experimental results indicated that leading-edge deflections of 30 and 40 degrees significantly reduce the magnitude of the wing effective dihedral relative to the baseline for a specified angle of attack or lift coefficient. For angles of attack greater than 15 degrees, these flap deflections reduce the configuration directional stability despite improved vertical tail effectiveness. Asymmetric leading edge deflections are shown to be inferior to conventional ailerons in generating rolling moments. Asymmetric leading-edge deflections are effective in producing side force at moderate to high angles of attack. VORSTAB lateral-directional calculations provide ballpark estimates at low to moderate angles of attack. The theory does not account for vortex flow induced, vertical tail effects at high angles of attack and should not be used for this angle of attack region. The empirical formulae for predicting vortex burst effects are not reliable in their present form. Although the basic trends are correct, the magnitude of the predicted vortex burst effect is typically over-estimated. / 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.

The aerodynamic-structural-control design of a simplified wing and a forward-swept composite wing are studied. In the first example, the wing is modeled as a beam with a control surface near the wing tip. The torsional stiffness is the only physical property varying along the span. The aerodynamic model is based on strip theory, and the control model is based on output feed-back control. With the structural-control interaction being the main focus, two different approaches are taken for the simplified wing design: (1) a sequential approach, (2) an integrated approach. In each approach the wing is designed for minimum weight subject to divergence and control deflection constraints. The results of this study indicated that while the integrated approach produced a better design than the sequential approach, the difference was minimal. In the second example, a forward-swept composite wing is designed for a high subsonic transport aircraft. The structural analysis is based on finite-element method. The aerodynamic calculations are based on vortex-lattice method, and the control calculations are based on output feed-back control. The wing is designed for minimum weight subject to structural, aerodynamic/performance and control constraints. Efficient methods are used to calculate the control deflection and efficiency sensitivities which appear as second order derivatives in the control constraint equations. To suppress the aeroelastic divergence of the forward-swept wing, and to reduce the gross weight of the design aircraft, two separate cases are studied: (1) combined application of aeroelastic tailoring and active controls, (2) aeroelastic tailoring alone. The results of this study indicated that, for this particular example, aeroelastic tailoring is sufficient for suppressing the aeroelastic divergence, and the use of active controls was not necessary. / Ph. D.