Thesis (M.S.)--Auburn University, 2007. / Abstract. Includes bibliographic references (ℓ. 88-89)

Thesis (M.S.)--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references.

Thesis (M.S.)--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references (p. 83-85).

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND AERO / Bibliography: p. 131-132. / by Louis Howard Knotts. / M.S.

A slender body theory method developed for a body moving parallel to a wall in shallow water is extended to include angular orientation of the body to the wall. The method satisfies only the zero normal velocity condition on the external boundaries but does not take into account the effect of induced flows on the body itself. A spheroid and a Series 60, block .80 hull were the bodies studied. The side force and yaw moment on each body were determined numerically for varying angular orientation with respect to either a single wall or canal bank. For both cases results for a range of depths and wall separation distances are presented. It is found that the method gives good qualitative side force predictions for a body moving parallel to a wall, but is unable to correctly predict the yaw moment or the side force due to angular orientation. This result dictates the need for a more complex mathematical model to properly represent the flow than the simple model and quasi'steady method used here. / Master of Science

Thesis (MScEng)-- Stellenbosch University, 2013. / ENGLISH ABSTRACT: This thesis presents the development of a flight control system (FCS) for an unmanned, unpowered parafoil and the integration with an existing parafoil system in collaboration with a team at the University of Cape Town (UCT). The main goal of the FCS is to autonomously guide the parafoil from an arbitrary deployment position to a desired landing target. A nonlinear 8 degrees of freedom (8-DOF) parafoil model by C. Redelinghuys is incorporated into a MATLAB Simulink simulation environment. The non-linear model is numerically linearised and modal decomposition techniques are used to analyse the natural modes of motion. All modes are determined to be stable but a poorly damped lateral payload relative twist mode is present which causes large payload yaw oscillations. The FCS is divided into stability augmentation, control and guidance subcomponents. Stability augmentation is proposed in the form of a yaw rate damper which provides artificial damping for the oscillatory payload twist mode. For control, a yaw rate controller is designed with the aim of a fast response while not exciting the payload twist oscillation. Subsequently, an existing guidance method is implemented for path following. Autonomous path planning and mission control logic is created, including an energy management (EM) method to eliminate excess height and a terminal guidance (TG) phase. The TG phase is the final turn before landing and is the last chance to influence landing accuracy. A TG algorithm is implemented which generates an optimal final turn and can be replanned en route to compensate for unknown wind and other disturbances. The FCS is implemented on existing avionics, integrated with the parafoil system and verified with hardware in the loop (HIL) simulations. Flight tests are presented but are limited to remote control (RC) tests that verify the integration of the avionics and the parafoil system and test preliminary FCS components. / AFRIKAANSE OPSOMMING: Hierdie tesis dra die ontwikkeling voor van ‘n vlug-beheerstelsel (VBS) vir ’n onbemande, onaangedrewe valskerm-sweeftuig (parafoil), asook die integrasie daarvan met ’n bestaande stelsel. Die projek is in samewerking met ’n span van die Universiteit van Kaapstad (UCT) uitgevoer. Die VBS se hoof doel is om die sweeftuig outonoom vanaf ’n arbitrêre beginpunt na ’n gewensde landingsteiken te lei. ’n Nie-lineêre 8 grade van vryheid sweeftuig model deur C. Redelinghuys is in die MATLAB Simulink omgewing geïnkorporeer. Die nie-lineêre model is numeries gelineariseer om ’n lineêre model te verkry, waarna die natuurlike gedrag van die tuig geanaliseer is. ’n Swak gedempte laterale draai ossillasie van die loonvrag is geïdentifiseer. Die VBS is opgedeel in stabiliteitstoevoeging, beheer en leiding. ’n Giertempo-demper (yaw rate damper) is as stabiliteitstoevoeging om die loonvrag ossillasie kunsmatig te demp, voorgestel. ’n Giertempo-beheerder is ontwerp met die klem op ’n vinnige reaksie terwyl die opwekking van die loonvrag ossillasie terselfdetyd verhoed word. Daarna is ’n bestaande metode vir trajekvolging geïmplementeer. Outonome padbeplanning en oorhoofse vlugplan logika is ontwikkel, insluitend ’n energie-bestuur (EB) metode, om van oortollige hoogte ontslae te raak, asook ’n terminale leiding (TL) metode. Die TL fase verwys na die finale draai voor landing en is die laaste kans om die landingsakkuraatheid te beïnvloed. ’n Bestaande TL algoritme is geïmplementeer wat ’n optimale trajek genereer en in staat is om vir wind en ander versteurings te kompenseer deur die trajek deurgaans te herbeplan. Die VBS is op bestaande avionika geïmplementeer, met die sweeftuigstelsel geïntegreer en met behulp van hardeware in die lus (HIL) simulasies geverifieer. Vlugtoetse is voorgedra, maar is egter beperk tot radio beheer vlugte wat die korrekte integrasie van die avionika en die voertuig toets, asook ’n beperkte aantal voormalige VBS toetse.

Near wake is the region of wake flow just behind the trailing edge of the body where the flow is strongly influenced by the upstream flow conditions and also perhaps by the charac­teristics of the body. The present work is concerned with the study of the development of turbulent near wake behind an infinitely yawed flat plate. The turbulent near wake behind an infinitely yawed flat plate is the simplest of the three-dimensional turbulent near wake flows. The present study aims at providing a set of data on the turbulent near wake behind an infinitely yawed flat plate and also at understanding the development and structure of the near wake. Detailed measurements of mean and turbulent quantities have been made using 3-hole probe, X-wire and 3-wire hotwire probes. Further an asymptotic analysis of the two-dimensional turbulent near wake flow has been formulated for the near wake behind an infinitely yawed flat plate. The feature that the near wake which is dominated by mixing of the oncoming turbulent boundary layer retains, to a large extent, the memory of the turbulent structure of the boundary layer, has been exploited to develop this analysis. The analysis leads to three regions of the wake flow (the inner near wake, the outer near wake and the far wake) for which the governing equations are derived. The matching conditions among these regions lead to logarithmic variations in both normal and longitudinal directions in the overlapping regions surrounding the inner wake. These features are validated by the present results. A computational study involving seven well known turbulence models was also under­taken in order to assess the performance of the existing turbulence models in the prediction of the turbulent near wake behind an infinitely yawed flat plate. In this study all the seven models are implemented into a common flow solver code, thus eliminating the influence of grid size, initial conditions and different numerical schemes while making the comparison. This study shows that the K - e model performs better than other models in predicting the near wake behind an infinitely yawed flat plate.