Browsing by Author "Martin, Peter"

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    Geometry parametrization and aerodynamic characteristics of axisymmetric afterbodies
    (AIAA, 2020-01-05) Zuccolo, Giovanni; MacManus, David G.; Goulos, Ioannis; Martin, Peter
    A key aspect of the preliminary design process for a new generation combat aircraft is the prediction of afterbody aerodynamic drag. Current prediction methods for preliminary design are constrained in terms of number of independent geometric degrees of freedom that can be studied due to the classic circular arc or conical afterbody geometry parametrization. In addition, the amount of data available for the construction of the reliable performance correlations is too sparse. This paper presents a methodology for the generation of aerodynamic performance maps for transonic axisymmetric afterbody and exhaust systems. It uses a novel parametric geometry definition along with a compressible flow solver to conduct an extensive design space exploration. The proposed geometry parametrization is based on the Class Shape Transformation method and it enables the assessment of the aerodynamic performance of a wider range of afterbodies at the expense of one additional geometric degree of freedom. Relative to the conventional approach, this enables the exploration of a wider design space and the construction of more complete aerodynamic performance maps. This research quantifies the impact of a number of geometric degrees of freedom on the aerodynamic performance of transonic afterbody and exhaust systems at different operating conditions.
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    Low order models for transonic afterbody aerodynamic characteristics
    (AIAA, 2020-01-05) Zuccolo, Giovanni; Christie, Robert; MacManus, David G.; Goulos, Ioannis; Martin, Peter
    A key aspect in the preliminary design of new combat aircraft is the prediction of the afterbody and exhaust system aerodynamic drag. To meet the various operating conditions requirements for a multi-role vehicle the afterbody typically includes a variable geometry. Within the preliminary design context, this makes the aerodynamic performance prediction a difficult challenge. This research investigates reduced order models for prediction of the aerodynamic performance of axisymmetric transonic afterbody and nozzle systems for a range of aerodynamic conditions and geometric degrees of freedom. The aerodynamic performance metric of interest is afterbody drag coefficient (CD). Two reduced order models are investigated: artificial neural network and Gaussian process. The geometric variables include boattail closing angle, nozzle throat to exit area ratio and afterbody mean angle and the aerodynamic parameters are free-stream Mach number and nozzle pressure ratio. The results show that these types of reduced order models can be used for preliminary design aerodynamic performance prediction. The Gaussian process CD prediction is less accurate compared to the artificial neural network with the latter giving a prediction uncertainty of approximately ±0.01 in CD with a 2σ confidence level. The Gaussian process prediction uncertainty is approximately ±0.013 CD.
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    Low-altitude unmanned aerial vehicles for the rapid and high-resolution determination of contamination
    (Cranfield University, 2016-12-06 11:29) Martin, Peter
    Poster presentation at the 2016 Defence and Security Doctoral Symposium. Following the events of March 2011 at the Fukushima Daiichi Nuclear Power Plant (FDNPP), a considerable quantity of radiation was released into the local Japanese as well as the global environment. Much work and expense is currently being devoted to the remediation of a large area of eastern Japan contaminated primarily by radiocaesium. Due to the complex nature of the environment affected by the release, it is important to understand contaminant evolution/migration at the greatest possible resolution –  previous airborne survey methods have lacked this high spatial resolution. Initially after the incident, a primary survey of contamination was performed by the US Department of Energy (US DoE) in collaboration with the Japanese MEXT producing a resolution of hundreds of meters per pixel. This survey illustrated the large-scale trend of the contamination influencing the initial evacuation of those in immediate risk. Increased resolution was provided by unmanned helicopters over the years since the event, reducing the pixel size down to a 24 m radius. The work presented here is the combined use of a low altitude multirotor unmanned aerial vehicle (UAV) coupled with a lightweight radiation detection and mapping system. Using this platform, it was possible to measure the current distribution of radionuclide contamination in Japan at a resolution greater than that previously achievable, with sub-meter resolution. Unlike ground-based surveys conducted on foot by humans, such a system eliminates the potentially large dose that would otherwise be received. With billions of dollars set to be spent on remediation over the coming years; it is crucial to determine the eventual fate and environmental pathways of various radionuclides. It is hoped that this technique will ultimately lead to a better understanding of the hazard, allowing those displaced to return to their homes. As a tool, this instrument is invaluable in locating, as well as identifying the specific isotopic composition of radioactive material, across a range of environments. In addition to locating and quantifying the contamination resulting from a nuclear incident such as Fukushima, the technology has numerous potential applications within the wider nuclear and defence industries. With the potential to assist in the routine monitoring of sites through to the post operational clean-out or in the aftermath of the deliberate dispersion of radioactive material and its associated trafficking.