Browsing by Author "Pelteret, Jean-Paul"

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    A CFD investigation of cavitation and associated deposit formation in modern diesel fuel injectors
    (2007) Pelteret, Jean-Paul; Yates, Andrew
    Reducing the pollution of new vehicles has become a priority to vehicle manufacturers, particularly given the fact that emissions requirements that must be achieved by diesel vehicles are becoming more stringent. Modem fuel injectors on common-rail diesel vehicles use very high rail pressures to aid atomisation and increase combustion efficiency. However, associated with the high injections pressures is the issue of nozzle cavitation. Cavitation leads to pockets of diesel vapour forming in the nozzle and it is hypothesised that this causes the formation of deposits in the nozzle. It is also suggested that the collapse of the cavitation vapour space results in extremely high temperatures within the nozzle, resulting in thermal cracking of the fuel and eventually the formation of carbon deposits. A two-dimensional axisymmetric CFD model with dimensions representative of an injector nozzle was constructed using a fully structured grid.
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    Open Access
    A computational neuromuscular model of the human upper airway with application to the study of obstructive sleep apnoea
    (2014) Pelteret, Jean-Paul; Reddy, B Daya
    Numerous challenges are faced in investigations aimed at developing a better understanding of the pathophysiology of obstructive sleep apnoea. The anatomy of the tongue and other upper airway tissues, and the ability to model their behaviour, is central to such investigations. In this thesis, details of the construction and development of a three-dimensional finite element model of soft tissues of the human upper airway, as well as a simplified fluid model of the airway, are provided. The anatomical data was obtained from the Visible Human Project, and its underlying micro-histological data describing tongue musculature were also extracted from the same source and incorporated into the model. An overview of the mathematical models used to describe tissue behaviour, both at a macro- and microscopic level, is given. Hyperelastic constitutive models were used to describe the material behaviour, and material incompressibility was accounted for. An active Hill three-element muscle model was used to represent the muscular tissue of the tongue. The neural stimulus for each muscle group to a priori unknown external forces was determined through the use of a genetic algorithm-based neural control model. The fundamental behaviour of the tongue under gravitational and breathing-induced loading is investigated. The response of the various muscles of the tongue to the complex loading developed during breathing is determined, with a particular focus being placed to that of the genioglossus. It is demonstrated that, when a time-dependent loading is applied to the tongue, the neural model is able to control the position of the tongue and produce a physiologically realistic response for the genioglossus. A comparison is then made to the response determined under quasi-static conditions using the pressure distribution extracted from computational fluid-dynamics results. An analytical model describing the time-dependent response of the components of the tongue musculature most active during oral breathing is developed and validated. It is then modified to simulate the activity of the tongue during sleep and under conditions relating to various possible neural and physiological pathologies. The retroglossal movement of the tongue resulting from the pathologies is quantified and their role in the potential to induce airway collapse is discussed.