Browsing by Author "Shires, Andrew"
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Item Open Access Analysis and prediction of the low speed flow over a highly swept wing(2000-11) Shires, Andrew; Garry, Kevin P.; Fulker, J. L.A combined experimental and theoretical study is described of the low speed flow over a highly swept and cambered wing that simulates the flow features of a transonic manoeuvre condition. The thesis is divided into two parts: Part I examines the research objectives from a customer perspective, with background information on the project history and funding sources. Since the research is aimed at improving the aerodynamic performance of low observable configurations, stealth technologies are discussed and their implications for combat aircraft wing flows. The management chapter of the thesis then discusses the influences affecting the decision making process for the acquisition of weapon systems in the UK. Part II describes the design of a highly swept and cambered wing that generates strong adverse pressure gradients near the trailing edge, leading to three-dimensional separations in this region. Using surface flow visualisation the nature of these flows is defined, indicating how the position of a separated streamline moves forward with increasing angle of incidence. These observations are confirmed by flow predictions using the SAUNA Computational Fluid Dynamics (CFD) method that solves the Reynolds Averaged Navier-Stokes equations, employing a two-equation turbulence model. The mechanism of the flow separation is also predicted using CFD, indicating that a separated stream surface reattaches at the wing trailing edge, forming a ‘tunnel’ of separated flow. To the authors knowledge this represents the first time that the main physical features of such a complex three-dimensional separated flow has been modelled using a CFD method. From an evaluation of the CFD methods employed, a design process has been proposed by which a wing designer can determine if wing flows over similar configurations remain attached. Additionally, the velocity magnitudes within parts of the separated shear layers and the wake are obtained using an optical non-intrusive measurement technique and give good agreement with the theory. -Item Open Access Application of Circulation Controlled Blades for Vertical Axis Wind Turbines(MDPI AG, 2013-07-26T00:00:00Z) Shires, Andrew; Kourkoulis, VelissariosThe blades of a vertical axis wind turbine (VAWT) rotor see an inconsistent angle of attack through its rotation. Consequently, VAWT blades generally use symmetrical aerofoils with a lower lift-to-drag ratio than cambered aerofoils tailored to maximise horizontal axis wind turbine rotor performance. This paper considers the feasibility of circulation controlled (CC) VAWT blades, using a tangential air jet to provide lift and therefore power augmentation. However CC blade sections require a higher trailing-edge thickness than conventional sections giving rise to additional base drag. The choice of design parameters is a compromise between lift augmentation, additional base drag as well as the power required to pump the air jet. Although CC technology has been investigated for many years, particularly for aerospace applications, few researchers have considered VAWT applications. This paper considers the feasibility of the technology, using Computational Fluid Dynamics to evaluate a baseline CC aerofoil with different trailing-edge ellipse shapes. Lift and drag increments due to CC are considered within a momentum based turbine model to determine net power production. The study found that for modest momentum coefficients significant net power augmentation can be achieved with a relatively simple aerofoil geometry if blowing is controlled through the blades rotation.Item Open Access Development and evaluation of an aerodynamic model for a novel vertical axis wind turbine concept(MDPI AG, 2013-05-15T00:00:00Z) Shires, AndrewThere has been a resurgence of interest in the development of vertical axis wind turbines which have several inherent attributes that offer some advantages for offshore operations, particularly their scalability and low over-turning moments with better accessibility to drivetrain components. This paper describes an aerodynamic performance model for vertical axis wind turbines specifically developed for the design of a novel offshore V-shaped rotor with multiple aerodynamic surfaces. The model is based on the Double-Multiple Streamtube method and includes a number of developments for alternative complex rotor shapes. The paper compares predicted results with measured field data for five different turbines with both curved and straight blades and rated powers in the range 100-500 kW. Based on these comparisons, the paper proposes modifications to the Gormont dynamic stall model that gives improved predictions of rotor power for the turbines considered.