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Browsing by Author "University of Virginia"

Now showing 1 - 18 of 18
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    Analysis of Tower Shadow Effects on the UAE Rotor Blades
    Noyes, Carlos; Loth, Eric; Qin, Chao (Virginia Tech, 2015-06)
    A leading obstacle hindering the development of wind turbines to extreme scale is the structural integrity of the blades. Downwind rotors have been shown to give structural advantages for larger systems. However, there is an added aerodynamic complication from the tower shadow. This paper presents and analyzes a previously unpublished subset of data collected by NREL during an extensive wind tunnel campaign for Unsteady Aerodynamic Experiment Phase VI (UAE Phase VI). The experimental data includes relative flow fields, aerodynamic blade forces, and root blade flapwise bending moments, from upwind turbines, downwind turbines and downwind turbines with the use of an aerodynamic tower fairing. It is shown that the tower shadow can have a severe and negative effect on these variables, leading to higher bending stresses. The use of a tower fairing can greatly reduce these detrimental effects. To better interpret this data, predictions using an aeroelastic wind turbine code, FAST, was used to model the experimental conditions. The differences between the experimental data and the computational predictions are attributed to unsteady effects of the wake. This suggest that wake modeling for downwind turbines may require modifications to capture physically realistic tower shadow effects.
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    Banner from University of Virginia
    University of Virginia (Digital Library and Archives, University Libraries, Virginia Tech, 2012-03-12)
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    Banner from University of Virginia
    University of Virginia (Digital Library and Archives, University Libraries, Virginia Tech, 2012-03-12)
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    Card from the Spanish House at University of Virginia
    University of Virginia (Digital Library and Archives, University Libraries, Virginia Tech, 2012-03-12)
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    Cover of The University of Virginia Magazine, Summer 2007, Vol. XCVI, No. 2
    University of Virginia (Digital Library and Archives, University Libraries, Virginia Tech, 2012-03-12)
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    Investigation of Dynamic Loading for 13.2 MW Downwind Pre-Aligned Rotor
    Qin, Chao; Loth, Eric; Lee, Sang; Moriarty, Patrick (Virginia Tech, 2015-06)
    To alleviate the mass-scaling issues associated with conventional upwind rotors of extreme-scale turbines, a downwind rotor concept is considered that uses fixed coning to align the non-circumferential loads for a given steady-state condition. This alignment can be pre-set to eliminate downwind blade moments for a given steady-state condition at rated wind speed and to minimize them for other conditions. The alleviation in downwind dynamic loads may enable a reduced structural blade mass as compared with a conventional upwind rotor. To examine the potential impact of this design, FAST simulations were conducted for a 13.2 MW rated turbine at steady-state conditions for two rotor configurations with similar power outputs: 1) a conventional upwind rotor with three blades and 2) a downwind pre-aligned rotor with two blades. The rotor mass was reduced by approximately 25% for the downwind pre-aligned configuration. In addition, the damage equivalent loads on the blades were reduced more than 60% for the downwind pre-aligned configuration. However, additional work is needed to investigate this concept at turbulent inflow conditions and for extreme events.
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    Photograph from University of Virginia
    University of Virginia (Digital Library and Archives, University Libraries, Virginia Tech, 2012-03-12)
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    Poster from University of Virginia
    University of Virginia (Digital Library and Archives, University Libraries, Virginia Tech, 2012-03-12)
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    Poster from University of Virginia
    University of Virginia (Digital Library and Archives, University Libraries, Virginia Tech, 2012-03-12)
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    Poster from University of Virginia
    University of Virginia (Digital Library and Archives, University Libraries, Virginia Tech, 2012-03-12)
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    Poster from University of Virginia
    University of Virginia (Digital Library and Archives, University Libraries, Virginia Tech, 2012-03-12)
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    Poster from University of Virginia
    University of Virginia (Digital Library and Archives, University Libraries, Virginia Tech, 2012-03-12)
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    Poster from University of Virginia
    University of Virginia (Digital Library and Archives, University Libraries, Virginia Tech, 2012-03-12)
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    Poster from University of Virginia
    University of Virginia (Digital Library and Archives, University Libraries, Virginia Tech, 2012-03-12)
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    Poster from University of Virginia
    University of Virginia (Digital Library and Archives, University Libraries, Virginia Tech, 2012-03-12)
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    Poster from University of Virginia
    University of Virginia (Digital Library and Archives, University Libraries, Virginia Tech, 2012-03-12)
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    Wind Turbine Tower Fairing Geometries to Decrease Shadow Effects
    Noyes, Carlos; Loth, Eric; Fuhrman, Jay (Virginia Tech, 2015-06)
    Tower fairings are a promising method to reduce wake for down wind turbines, with the drawback that the performance may be lost at high angles of attack. For example, the E863 airfoil has a much smaller wake than a cylinder at 0° but a similar wake at 20°. This study investigates various fairing geometries focusing on impact of a rounded trailing edge on the wake for an angle of attack of 20°. Models were designed and manufactured of the E863 fairing and two fairings with circularly rounded trailing edges, E863r40 and E863r45. The modified fairings having a thickness ratio of 40% and 45% respectively. The fairings were tested in a water tunnel at Reynolds number based on diameter of 6.82x104 using dye for flow visualization and particle image velocimetry for wake quantification. Instantaneous, averaged and root mean squared values of velocity deviation and flow angle were analyzed for all the models. It was shown that both of the modified trailing edge fairings (with rounding) performed better than the unmodified aerodynamic fairing at 20°. In particular, the E863r45 performed better than the E863r40 and performed comparably to the cylinder at 20°. However at 0°, the E863 and the E863r40 showed little wake instability, and were better than the E863r45 (and far better than the cylinder).