Comparison of BEM and CFD results for MEXICO rotor aerodynamics

• We compute aerodynamics forces in MEXICO wind turbine rotor, by mean of two different codes.
• A discussion of these results in comparison with experimental data from wind tunnel tests is done.
• BEM code gives good results in Forces at low wind speed, and very bad at high wind speed.
• CFD code present good results in all the wind speed range, although time of calculation is as far higher.
• Some CFD data like pressures and 3D effects is studied to support discussion of results.

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 and 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.