Comparison of BEM and CFD results for MEXICO rotor aerodynamics

Abstract

This work aims to conduct an aerodynamic analysis of the MEXICO wind turbine rotor, establishing comparisons between the results of two radically different computational techniques and measurements, obtained in wind tunnel tests under controlled conditions in the framework of the MEXICO project (Boorsma and Schepers, 2009, Schepers et al., 2012). Forces, pressures, and torque generated in the rotor are computed usingthe blade element momentum (BEM) and computational fluid dynamics (CFD) codes to investigate their main strengths and weaknesses at different wind speeds, highlighting the quality of the results obtained at different blade stations. In general terms, both methods tend to overestimate the spanwise distribution of forces and pressures. Reynolds-averaged Navier–Stokes (RANS)-CFD simulations maintain a uniform level of accuracy across the studied velocity range, whereas BEM calculations outperform CFD estimates at low wind velocities but fail at higher velocities due to separated flow conditions. Blade tip loss and three-dimensional (3D) effects are partly responsible for inaccuracies in calculation, especially for the BEM code. These 3D effects are discussed briefly in relation to force estimates.