No description available.

No description available.

The effect of sweep on separation bubbles as occurring in the subsonic flows past thin flat plates with rectangular leading edges has been studied experimentally. The distance between separation and reattachment, at high Reynolds number, was about 5.5 times the plate thickness in the flow region undisturbed by end effects. This distance was independent of sweepback for sweep angles up to and including 45<SUP>o</SUP>. The chordwise distribution of a static-pressure coefficient and a coefficient of the intensity of the static-pressure fluctuations, both measured on the surface of the plate and based upon the free-stream velocity component normal to the leading edge, were independent of the sweep angle up to and including 30<SUP>o</SUP> to a first approximation. The spectra of the static-pressure fluctuations, however, displayed some qualitative changes with increasing sweep angle. The distribution of a coefficient of the chordwise skin-friction component, based upon the free-stream velocity component normal to the leading edge, was independent of sweep up to and including 30<SUP>o</SUP> to a crude first approximation. The chordwise velocity profiles non-dimensionalised by the local external chordwise velocity component, were independent of sweep up to and including 45<SUP>o</SUP> in the separation bubble but downstream of reattachment small but persistent changes occurred with increasing sweep angle. Smoke-flow visualisations in the swept and the unswept flow at low Reynolds number displayed the presence of typical vortex loops in the reattachment region, many of which broke up and were partially entrained into the separation bubble.

A computational investigation was performed to assess the effectiveness of Detached-Eddy Simulation (DES) as a tool for predicting icing effects. The AVUS code was employed to compute solutions for an iced wing configuration using DES and steady-state Reynolds Averaged Navier-Stokes (RANS) equation methodologies. The model wing was an extruded GLC305/944-ice shape section with a rectangular planform. Unstructured grids were generated using VGRID/GRIDTOOL. The one-equation Spalart-Allmaras turbulence model was used for all steady state RANS and DES computations. The numerical results were evaluated by comparison with experimental data. RANS solutions significantly under-predicted the lift and drag even after mesh refinement. The time-averaged DES computations showed some improvement in lift and drag coefficients, when compared to experimental data near stall at a 6 deg angle of attack. No significant improvement was observed at lower angles of attack. The DES computations were determined to be valid, since significant changes in the flow field were not observed after both mesh refinement and time step refinement.

No description available.

No description available.

In this study, a design procedure incorporating a genetic algorithm (GA) is developed for optimization of the wing structure of a two seated trainer aircraft with single turboprop engine. The objective function considered is the total weight of the structure. The objective function is minimized subjected to certain strength requirements. In order to evaluate the design constraints and model the wing structure, finite element analysis is performed by using a conventional finite element solver (i.e. MSC/NASTRAN&reg / ). In addition, MSC/PATRAN&reg / commercial package program is used as preprocessor and postprocessor tool. VISUAL FORTRAN programming language is also utilized as the genetic algorithm implementation tool. Several conclusions drawn from the optimization results are presented.

abstract: Modern aircraft are expected to fly faster and more efficiently than their predecessors. To improve aerodynamic efficiency, designers must carefully consider and handle shock wave formation. Presently, many designers utilize computationally heavy optimization methods to design wings. While these methods may work, they do not provide insight. This thesis aims to better understand fundamental methods that govern wing design. In order to further understand the flow in the transonic regime, this work revisits the Transonic Similarity Rule. This rule postulates an equivalent incompressible geometry to any high speed geometry in flight and postulates a “stretching” analogy. This thesis utilizes panel methods and Computational Fluid Dynamics (CFD) to show that the “stretching” analogy is incorrect, but instead the flow is transformed by a nonlinear “scaling” of the flow velocity. This work also presents data to show the discrepancies between many famous authors in deriving the accurate Critical Pressure Coefficient (Cp*) equation for both swept and unswept wing sections. The final work of the thesis aims to identify the correct predictive methods for the Critical Pressure Coefficient. / Dissertation/Thesis / Masters Thesis Aerospace Engineering 2016

The thesis deals with the issue of replacement of the Rotax 912 ULS engine with the Rotax 915 iSc3 B engine and its impact on flight performance, characteristics and airframe loads of the WT 9 Dynamic. For accomplish better maneuverability tail surfaces are enlarged. Both versions of airplane with different engines and tails surfaces are quantified with respect to airframe loads and flight characteristics. The output of the diploma thesis can be used for strength design of airplane structure and stress tests of the new modification of the WT 9 Dynamic aircraft.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: This thesis forms part of the Control Surfaces in Confined Spaces (CoSICS) project conducted at Stellenbosch University. The aim of this project is reduction of control surface actuator footprints on the existing wing structures of commercial airliners such as the Airbus A320 and A330. This is achieved by reducing control surface hinge moments through the application of trailing edge tabs. This results in smaller actuator requirements. The first tier of the project focussed on the geometric optimisation of the tab applied to an aileron. This thesis focusses on the development of dynamic control of the aileron through either tab-only or concurrent tab and aileron actuation. In the effort to develop dynamic control, a fully coupled generalised dynamic model of the tab and aileron is derived and presented. Through linearisation of this model, linear controllers are developed. Two distinctly different controllers are presented; the first controller makes use of classical methods for control of the tab-only actuated aileron and the second controller makes use of modern control techniques such as full state feedback to facilitate controlled concurrent tab and aileron actuation. Each proposed controller is evaluated in terms of dynamic performance, robustness, disturbance rejection and noise immunity. Based on the controller development, a summary of dynamic actuator requirements is given. Practical verification of the model and the controller performance is then undertaken. The development of the necessary hardware and software is also presented. The concept of aileron control through tab-only actuation and concurrent tab and aileron actuation is then validated. Conclusion are then drawn about the accuracy of the theoretical model and the practical performance of the controllers. The thesis is concluded with recommendations for future work to increase the fidelity of the model. Important aspects about the practical implementation of the concept on commercial jetliners are also summarised. / AFRIKAANSE OPSOMMING: Hierdie tesis is deel van die Control Surfaces in Confined Spaces1 projek by Stellenbosch Universiteit. Die doel van hierdie projek behels die verkleining van die aktueerder spasie en ondersteunings struktuur vereistes, op die bestaande vlerk struktuur van kommersiële vliegtuie soos die Airbus A320 en Airbus A330. Dit is bereik deur die vermindering van die beheeroppervlak skarnier se draaimoment met behulp van aerodinamiese hulpvlakke. Kleiner aktueerders word dus benodig. Die eerste stadium van die projek fokus op die geometriese optimisering van die hulpvlak op ’n aileron. Hierdie tesis fokus op die ontwikkeling van dinamiese beheer van die aileron deur middel van hulpvlak aktueering alleenlik of met die gelyktydige aktueering van die hulpvlak en aileron. In die proses van onwikkeling is ’n volgekoppelde veralgemeende dinamiese model van die hulpvlak en aileron afgelei en voorgelê. Deur middel van linearisasie van die model is linieêre beheerders ontwikkel. Tans is twee verskillende beheerders ontwikkel. Die eerste beheerder is gebaseer op die klassieke metodes en maak staat op die aktueering van die hulpvlak alleenlik. Die tweede beheerder maak gebruik van moderne beheer tegnieke soos vol toestand terugvoer om gelyktydige hulpvlak en aileron aktueering te realiseer. Die beheerders is elk geëvalueer in terme van dinamiese gedrag, robuustheid, versteurings verwerping en ruis verwerping. Die beheerstelsel ontwikkeling lei tot ’n opsomming van die dinamiese aktueerder vereistes. Dit word gevolg deur praktiese verifikasie van die model en die beheerstelsel gedrag. ’n Opsomming van die ontwikkeling van nodige hardeware en sagteware word voorgelê. In hierdie proses is die konsep van beide hulpvlak alleenlike aktueering en gelyktydige hulpvlak en aileron aktueering bewys. Gevolgtrekkings word gemaak oor die akkuraatheid van die model en die praktiese gedrag van die beheerders. Die tesis word afgerond met voorstelle vir toekomstige werk wat die model se betroubaarheid kan verbeter. Verder word belangrike punte oor die praktiese aspekte van konsep implementering op kommersiële vliegtuie ook uitgelig.