Wind Turbine Tower Fairing Geometries to Decrease Shadow Effects

Abstract

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).