Browsing by Author "Noyes, Carlos"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
- Analysis of Tower Shadow Effects on the UAE Rotor BladesNoyes, 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 This paper presents and analyzes a previously unpublished subset of data collected by NREL during an extensive wind tunnel campaign for Unsteady Aerodynamic Experiment Phase VI (UAE Phase VI).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.
- Wind Turbine Tower Fairing Geometries to Decrease Shadow EffectsNoyes, 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).