Small horizontal axis wind turbine: analytical blade design and comparison with RANS-predicted flow field and performance data

Authors

T. Gerhard, T.H. Carolus - University of Siegen, Germany

Abstract

An analytical method for designing axial wind turbine blades is described. It is based on the classical blade element momentum (BEM) model, but formulated in terms of velocity triangles, Euler’s turbine equation, and the vector mean velocity from in- to outlet in the rotating frame of reference. Airfoil lift and drag are determined via XFOIL. A small axial wind turbine is designed by means of this analytical tool. Then a 3D RANS simulation at design operation is performed. For turbulence modeling we use the standard shear stress transport, and, alternatively, a laminar/turbulent transition model. Local values such as the induction factors, the pressure distributions and integral performance data are compared. Although the blade boundary layer is basically transitional, the accuracy of the numerical results utilizing the laminar/turbulent transition model and the shear stress transport model is similar as compared to the analytical design target.