The interaction of an unsteady wake with a solid body can induce sizable loading of the structure, which has many detrimental side effects in both the structural and acoustic senses. These interactions are ubiquitous in nature and engineering. A flow control technique is sought to mitigate this interaction, thereby decreasing the level of structural vibration. This thesis investigates the effectiveness of steady leading-edge blowing (LEB) flow control for modifying the vortex induced vibrations on an airfoil in the wake of a circular cylinder. The airfoil was allowed to oscillate perpendicular to the fluid flow direction in response to the impinging Von-Karman vortex street. The flow field and airfoil vibrations were simultaneously captured using Digital Particle Image Velocimetry (DPIV) and accelerometer measurements in a time-resolved sense. The results indicate that LEB can significantly reduce the degree of unsteady loading due to the blade vortex interaction (BVI). In some cases, the LEB jet appears to break the coherency of a vortex incident on the airfoil, and in other cases the jet increase the mean stand-off distance of the vortex as it convects over the airfoil surface. It was also found that, for large circular cylinders, if the airfoil is within the mean closure point of the circular cylinder wake, the LEB can increase the level of BVI. The Proper Orthogonal Decomposition (POD) was also used to analyze the DPIV data. POD is mathematically superior for reducing a data rich field into fundamental modes; a suitable basis function for the reduction is chosen mathematically and it is not left to the researcher to pick the basis function. A comparison of the energy in these modes is useful in ascertaining the dynamics of the BVI. For one of the two cases examined with POD, it was found for no LEB the fundamental (i.e. most energetic) mode is given by the vortex shedding of the circular cylinder upstream. The addition of LEB reduces the energy contained in this fundamental mode. Thus the LEB jet has the effect of reducing the flow field coherency; the structure of the large vortices is broken up into smaller vortices. For the other case, the LEB jet has the opposite effect: the jet has the ability to organize the circular cylinder wake into coherent structures. This acts to increase the coherency of the circular cylinder wake and increases the level of BVI. / Master of Science

This thesis documents trailing edge blowing research performed to reduce rotor / stator interaction noise in turbofan engines. The existing technique of filling every velocity deficit requires a large amount of air and is therefore impractical. The purpose of this research is to investigate new blowing configurations in order to achieve noise reduction with lesser amounts of air. Using the new configurations air is not injected into every fan blade, but is instead varied circumferentially. For example, blowing air may be applied to alternating fan blades. This type of blowing configuration both reduces the amount of air used and changes the spectral shape of the tonal interaction noise. The original tones at the blade passing frequency and its harmonics are reduced and new tones are introduced between them. This change in the tonal spectral shape increases the performance of acoustic liners used in conjunction with trailing edge blowing. This thesis presents numerical predictions performed to estimate the sound power reductions due to these concepts, as well as experimental results taken on the ANCF rig at NASA Glenn for validation purposes. The results show that the new concepts are successful in increasing the efficiency of trailing edge blowing. / Master of Science

Road vehicles are still largely a consumer product and as such the styling of a vehicle becomes a significant factor in how commercially successful a vehicle will become. The influence of styling combined with the numerous other factors to consider in a vehicle development programme means that the optimum aerodynamic package is not possible in real world applications. Aerodynamicists are continually looking for more discrete and innovative ways to reduce the drag of a vehicle. The current thesis adds to this work by investigating the influence of active flow control devices on the aerodynamic drag of square back style road vehicles. A number of different types of flow control are reviewed and the performance of synthetic jets and pulsed jets are investigated on a simple 2D cylinder flow case experimentally. A simplified ¼ scale vehicle model is equipped with active flow control actuators and their effects on the body drag investigated. The influence of the global wake size and the smaller scale in-wake structures on vehicle drag is investigated and discussed. Modification of a large vortex structure in the lower half of the wake is found to be a dominant mechanism by which model base pressure can be influenced. The total gains in power available are calculated and the potential for incorporating active flow control devices in current road vehicles is reviewed. Due to practicality limitations the active flow control devices are currently ruled out for implementation on a road vehicle. The knowledge gained about the vehicle model wake flow topology is later used to create drag reductions using a simple and discrete passive device. The passive modifications act to support claims made about the influence of in wake structures on the global base pressures and vehicle drag. The devices are also tested at full scale where modifications to the vehicle body forces were also observed.

In the military arena there is an increase in demand for Low Observable (LO) flight vehicles. This drive for low observability imposes limits on Leading Edge (LE) sweep angles and prohibits the use of a tailplane/fin resulting in unconventional configurations; a typical example of which are Unmanned Combat Aerial Vehicles (UCAVs). This class of aircraft poses stability and control problems due to the early onset of flow separation. The focus of this project is on the on the use of Tangential Leading Edge Blowing (TLEB) as a means of separation suppression on such vehicles. This project is unique in that the TLEB slot is positioned on the wing lower surface facing the oncoming freestream. Also, the model in this project is representative of the outboard panel of a UCAV wing, a geometry on which TLEB has not been explored in the past. A swept wing model (LE sweep = 47 degrees, AR = 3) was designed. The model has a TLEB nozzle with a slot on the lower surface at approx. 1% yawed chord that spans 0.58 m (approx. 70% LE length). Baseline wing characteristics were obtained with the full slot exposed. The wing showed a variation in pitch between CL = 0 and 0.6 which from oil flow visualisation is believed to be due to laminar separation. At CL = 0.6 there is a positive pitch break which flow visualisation suggests is due to the occurrence of a LE vortex. Sensitivity studies for slot configuration, Re number and transition fixing were carried out. The blowing rates 0.0025, 0.005, 0.025, 0.05 were tested for two slot lengths; one full span (0.58 m) and another third span positioned at the midpoint of the full slot. All blowing rates show some suppression of the LE vortex and therefore reduction in severity of the pitch break at CL = 0.6. High blowing rates produce a negative shift in CM, which CFD suggests is due to a large amount of suction produced on the lower wing surface adjacent to the slot exit. This means the available trim power is less than for the lower blowing rates. Wool tuft results for high blowing rates from the middle slot show an increase in streamwise flow at the TE suggesting TLEB is capable of improving the effectiveness of TE devices. The effectiveness of TLEB at low blowing rates has been shown to be high compared to that found in literature. A 1st order analysis of the impact of TLEB on a full scale system shows realistic options.

The objective of this study was mainly to describe, analyse and evaluate the determinants of the phenomenon of whistle blowing that influences the protection of employees making authorised and/or unauthorised disclosures. It was also a purpose of the study to evaluate the specific role of the Protected Disclosures Act 2000 (Act 26 of 2000) (PDA) in fulfilling its mandate to protect authorised disclosures on wrongdoing in public and private sector organisations. The PDA seeks to combat crime and corruption through the disclosing of wrongdoing. The intention is to create a culture which will facilitate the disclosure of information by employees relating to criminal and other irregular conduct in the workplace in a responsible manner, by providing comprehensive statutory guidelines through the PDA for the disclosure of such information, and protection against any retaliation as a result of such disclosures. An important aspect that this study dealt with was the provision, as a prerequisite to the PDA to be implemented successfully, that individual members of the private and public sectors have to act responsibly and in good faith in making disclosures in order to be protected by the PDA. In order to provide clarity on the conceptualisation of whistle blowing, the study explored the conceptual knowledge of the variables influencing the determinants of whistle blowing and the whistle blower through the application of a literature study of the concept and theories of ethics, values, morals, loyalty, trust and whistle blowing, in order to describe and analyse the variables influencing the whistle blower, the whistle blowing process, the characteristics of whistle blowers and the strategies and procedures employed to blow the whistle in an organisation. The study explored the organisational determinants influencing a whistle blower's decision to blow the whistle in the social context of an organisation in order to determine the influence of organisational culture and organisational trust as internal social factors that may facilitate the effective management of whistle blowing resulting in no whistle blowing taking place. The study objectives, appropriate conclusions and proposals are addressed based on the role that the PDA, the ethical determinants of the work environment, the determinants influencing the individual whistle blower and the organisational determinants influencing effective whistle blowing, can fulfil, in order to serve as a mechanism to combat corruption. / Public Administration / D. Litt. et Phil. (Public Administration)

The objective of this study was mainly to describe, analyse and evaluate the determinants of the phenomenon of whistle blowing that influences the protection of employees making authorised and/or unauthorised disclosures. It was also a purpose of the study to evaluate the specific role of the Protected Disclosures Act 2000 (Act 26 of 2000) (PDA) in fulfilling its mandate to protect authorised disclosures on wrongdoing in public and private sector organisations. The PDA seeks to combat crime and corruption through the disclosing of wrongdoing. The intention is to create a culture which will facilitate the disclosure of information by employees relating to criminal and other irregular conduct in the workplace in a responsible manner, by providing comprehensive statutory guidelines through the PDA for the disclosure of such information, and protection against any retaliation as a result of such disclosures. An important aspect that this study dealt with was the provision, as a prerequisite to the PDA to be implemented successfully, that individual members of the private and public sectors have to act responsibly and in good faith in making disclosures in order to be protected by the PDA. In order to provide clarity on the conceptualisation of whistle blowing, the study explored the conceptual knowledge of the variables influencing the determinants of whistle blowing and the whistle blower through the application of a literature study of the concept and theories of ethics, values, morals, loyalty, trust and whistle blowing, in order to describe and analyse the variables influencing the whistle blower, the whistle blowing process, the characteristics of whistle blowers and the strategies and procedures employed to blow the whistle in an organisation. The study explored the organisational determinants influencing a whistle blower's decision to blow the whistle in the social context of an organisation in order to determine the influence of organisational culture and organisational trust as internal social factors that may facilitate the effective management of whistle blowing resulting in no whistle blowing taking place. The study objectives, appropriate conclusions and proposals are addressed based on the role that the PDA, the ethical determinants of the work environment, the determinants influencing the individual whistle blower and the organisational determinants influencing effective whistle blowing, can fulfil, in order to serve as a mechanism to combat corruption. / Public Administration and Management / D. Litt. et Phil. (Public Administration)

The focus of this research was on the Management of Whistle-Blowing at the University of South Africa (UNISA). This study investigated the perception of UNISA staff on the issue of whistle-blowing. Using a quantitative approach, a questionnaire was used to obtain relevant information from permanent employees of UNISA, at all campuses and regions, regarding the issue of whistle-blowing. This study highlights the attitudes and opinions of permanent employees of UNISA regarding the issue of whistle-blowing, and whether or not these attitude and opinions can influence the effectiveness of whistle-blowing, as a crime and unethical conduct deterrent and detection mechanism. Several issues were investigated in this study, as whistle-blowing if implemented and managed correctly, can be a valuable source of intelligence on crime and unethical conduct in the workplace. / CRIMINOLOGY / MA (POLICE SCIENCE)

The focus of this research was on the Management of Whistle-Blowing at the University of South Africa (UNISA). This study investigated the perception of UNISA staff on the issue of whistle-blowing. Using a quantitative approach, a questionnaire was used to obtain relevant information from permanent employees of UNISA, at all campuses and regions, regarding the issue of whistle-blowing. This study highlights the attitudes and opinions of permanent employees of UNISA regarding the issue of whistle-blowing, and whether or not these attitude and opinions can influence the effectiveness of whistle-blowing, as a crime and unethical conduct deterrent and detection mechanism. Several issues were investigated in this study, as whistle-blowing if implemented and managed correctly, can be a valuable source of intelligence on crime and unethical conduct in the workplace. / CRIMINOLOGY / MA (POLICE SCIENCE)

No description available.

The study of the flow of a fan blade was conducted to improve tonal fan noise reduction by optimizing an existing flow control configuration. The current configuration consisted of a trailing edge Slot with a flow control area of 0.045 in² per inch span with an exit angle of -3.3° with respect to the blade exit angle. Two other flow control configurations containing discrete jets were investigated. For the first configuration, the trailing edge jets (TEJ), the fan blade was modified with discrete jets spaced 0.3 inches apart with a flow control area of 0.01 in² per inch span positioned on the trailing edge aimed at -3.3° with respect to the blade exit angle. Similarly, discrete jets were also placed on the suction surface at 95.5% chord aimed at 15° with respect to the local blade surface. This configuration is referred to as the suction surface jet (SSJ). The discrete jets for both configurations were designed to be choked while injecting a mass flow rate of 1.00% of the fan through-flow. Computational Fluid Dynamics (CFD) was used to model new configurations and study subsequent changes in total pressure deficit using a blade design inlet Mach number of 0.73, Reynolds number based on chord length of 1.67 à 106, and design incidence angle of 0°. Experimental testing was later conducted in a 2D cascade tunnel. The TEJ and SSJ were tested at design blowing of 1.00% and at off-design conditions of 0.50%, 0.75%, and 1.25% fan through-flow. Results between the different flow control configurations were compared using a blowing coefficient. CFD showed the TEJ and SSJ offered aerodynamic improvement over the Slot configuration. Testing showed the SSJ outperformed the TEJ, as validated in CFD, producing wider and shallower wakes. SSJ area-averaged pressure losses were 25% less than TEJ at design. Noise predictions based on CFD findings showed that both TEJ and SSJ provided additional tonal sound power level attenuation over the Slot configuration at similar blowing coefficients, with the SSJ providing the most attenuation. Noise prediction based on experimental results concurred that the SSJ provided more total attenuation than the TEJ. Experimental results showed that the SSJ performed better aerodynamically and, based on analytical prediction, provided 2 dB more total attenuation than the TEJ. / Master of Science