Browsing by Author "Wilson, Steven"
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Item Open Access Application of simplified numerical and analytical methods for rapid analysis in atmospheric entry vehicle design(AIAA Conference, 2015) Hinman, William; Johansen, Craig; Wilson, StevenSelected simplified numerical and analytical methods are applied to flow around hypersonic adiabatic blunt bodies. In particular, selected methods that are well defined in the literature, such as the modified Newton’s method, transformed finite difference grid in the shock layer, and the method of characteristics in the supersonic region, are utilized to solve the flow around an adiabatic circular cylinder at Mach 6. The results are compared to results obtained by numerical simulation of the compressible Navier-Stokes equations. The comparison is used to draw conclusions about the applicability and accuracy of these methods as they apply to low Reynolds number, small radius of curvature bodies such as atmospheric entry vehicles. A minor improvement to the results is proposed by the inclusion of an iterative interaction between the boundary layer displacement thickness, and the external inviscid free-stream.Item Open Access Compliance, Not Enforcement: A Comparative Evaluation of Best Practice Regulation for Hydraulic Fracturing(2015-09) Wilson, Steven; Mansell, RobertThe following study seeks to define and identify regulatory excellence for hydraulic fracturing with a focus on issues of compliance and enforcement. The inspiration for this investigation developed as a result of intense criticism and scrutiny of oil and gas regulators and their enforcement practices, both in Alberta, and throughout North America. These critiques have appeared predominantly in news media, as well as independent studies produced by think tanks and environmental advocacy organizations. The overwhelming consensus is that regulatory compliance, and any subsequent enforcement, is critically low. Regulatory agencies, it is said, are therefore failing in their mandates to adequately protect the environment and the public from hydraulic fracturing’s numerous associated environmental and human health risks. I wanted to find out for myself, through a critical, comprehensive evaluation, to what extent these allegations might be true. My findings reveal that while they certainly contain some merit, and do offer some worthwhile contributions on how compliance and enforcement may be improved, the overall analyses are constrained through an inadequate understanding of the intricacies of modern environmental regulation. I begin my study by outlining the numerous informational gaps and inherent controversies associated with the hydraulic fracturing debate, as well as providing both an environmental and an economic justification for strong regulatory oversight, including enforcement. By incorporating the University of Pennsylvania Law School’s recent Best In Class Regulator Initiative, I establish a comprehensive framework for assessing regulatory excellence. This framework includes key areas such as a regulator’s level of general expertise and its organizational structure, as well as notions of transparency, approaches to risk management, and the degree to which it promotes flexibility and adaptability to changing circumstances.Item Open Access Performance analysis of the Atlantis Intake System(AIAA Conference, 2015) Wilson, Steven; Johansen, Craig; Mravcak, VladimirA control volume analysis of a novel dynamic intake system known as the Atlantis Intake System (AIS) used to supply air and fuel to a ramjet engine has been performed. The AIS, being developed by Atlantis Research Labs, is based on the work of Eugene Gluhareff. Since Gluhareff ’s pressure jet design was originally intended for tip propulsion of helicopter rotor blades, it has been modified to work with a ramjet engine. The AIS utilizes three inlet stages where an under-expanded fuel jet is injected to draw in ambient air, producing a high velocity reactive mixture. Deceleration in a supersonic diffuser results in a high stagnation pressure gas mixture entering the combustion chamber. A method for the prediction of downstream mixture properties and resulting engine performance is derived for both static and dynamic operation. Performance is assessed in terms of specific impulse. The prediction models are validated against numerical simulations that replicate flow conditions associated with the AIS. Means of entrainment are studied through an analysis of the numerical simulation results.Item Open Access Performance evaluation of an overdriven LED for high-speed schlieren imaging(Journal of Visualization, 2015-02) Wilson, Steven; Gustafson, Garrett; Lincoln, Daniel; Murari, Kartik; Johansen, CraigA quantitative comparison of an overdriven light-emitting diode (LED) and a high-intensity discharge (HID) lamp as illumination sources for high-speed schlieren imaging is presented. A custom pulser circuit utilizing a new and improved driver circuit was developed to overdrive the LED by a factor of ten while simultaneously reducing pulse widths to sub-microsecond durations. The LED system has been developed as a simple and inexpensive alternative light source to discharge lamps and pulsed laser systems, which are typical for high-speed schlieren imaging. Image quality of a decaying spherical shock wave, produced from the unsteady release of an under-expanded helium jet, is analyzed to assess comparative performance. The effects of framing rate, camera exposure time, and pulse duration on image quality were assessed and compared for the novel LED and an HID. Framing rates of 10,000 and 50,000 fps and exposure times of 1 and 10 µs were tested. Image quality was assessed qualitatively through side-by-side comparisons of fluid dynamic features such as the resolution of shock waves, compression waves, and shear layers. Quantitative analysis was performed through the comparison of the signal-to-noise ratio at the various conditions. LED performance was found to be superior when imaging fast events and inferior when imaging slower events. Results and potential system improvements indicate that the LED system is ideal for low-cost, high-speed flow imaging.