Aerodynamic Improvements of Wind-Turbine Airfoil Geometries With the Prescribed Surface Curvature Distribution Blade Design (CIRCLE) Method

Abstract

The prescribed surface curvature distribution blade design (CIRCLE) method can be used for the design of two-dimensional (2D) and three-dimensional (3D) turbomachinery blade rows with continuous curvature and slope of curvature from leading edge (LE) stagnation point to trailing edge (TE) stagnation point and back to the LE stagnation point. This feature results in smooth surface pressure distribution airfoils with inherently good aerodynamic performance. In this paper the CIRCLE blade design method is modified for the design of 2D isolated airfoils. As an illustration of the capabilities of the method, it is applied to the redesign of two representative airfoils used in wind turbine blades: the Eppler 387 airfoil and the NREL S814 airfoil. Computational fluid dynamic analysis is used to investigate the design point and off-design performance of the original and modified airfoils, and compare with experiments on the original ones. The computed aerodynamic advantages of the modified airfoils are discussed. The surface pressure distributions, drag coefficients, and lift-to-drag coefficients of the original and redesigned airfoils are examined. It is concluded that the method can be used for the design of wind turbine blade geometries of superior aerodynamic performance.