Single and Multi Objective CFD Optimization of Horizontal Axis Wind Turbines

Abstract

In spite of the enlarging interest in wind turbines development, the design optimization of wind turbine blades has not been studied in the past as gas or steam turbines optimization. Due to its reduced computational cost, Blade Element Momentum (BEM) method has been employed up to now to estimate the power output of the turbine. However, BEM method is not able to predict complex three dimensional flow fields or the performance of profiles for which drag and lift coefficients are not available. Theoretically, Computational Fluid Dynamics (CFD) can be more useful in these cases, but at the price of a much higher overall computational cost. In a past work, the authors developed and validated a simplified CFD process (including meshing) capable to assess the aerodynamic loads acting on a wind turbine with acceptable computational resources. Starting from that, in this work a full 3D CFD optimization of a small wind turbine is presented, both with constrained single- and multi-objective. Twist and chord distributions of a single blade have been varied keeping fixed the aerodynamic profile, and the obtained optimums have been compared with a benchmark case. The results demonstrate that CFD optimization can be effectively employed in a wind turbine optimization. As expected, stalled conditions of the blade are more likely to be improved than those characterized by attached flow. Future works will focus on multi-disciplinary optimization and will include also aerodynamic profile variation.