Rotational augmentation disparities in the MEXICO and UAE Phase VI experiments

Abstract

Wind turbine structures and components suffer excessive loads and premature failures when key aerodynamic phenomena are not well characterized, fail to be understood, or are inaccurately predicted. Turbine blade rotational augmentation remains incompletely characterized and understood, thus limiting robust prediction for design. Pertinent rotational augmentation research including experimental, theoretical, and computational work has been pursued for some time, but large scale wind tunnel testing is a relatively recent development for investigating wind turbine blade aerodynamics. Because of their large scale and complementary nature, the MEXICO and UAE Phase VI wind tunnel experiments offer unprecedented synergies to better characterize and understand rotational augmentation of blade aerodynamics. Cn means, Cn standard deviations, two-dimensional cp distributions, and three-dimensional planform surface pressure topologies from these two experiments were analyzed and compared. Rotating blade data were evaluated against analogous stationary blade data. Rotational augmentation effects were found to be pervasive and were present over the blade radius and throughout blade operating envelopes at all radial locations investigated. Rotational effects manifested themselves in both mean and time varying statistics, in both two-dimensional sectional data as well as three-dimensional planform data. Comparative analyses of MEXICO and UAE data validated and generalized current knowledge regarding rotationally augmented blade flow fields. In addition to confirming prior research, results also provided new insights not attainable by considering either data set in isolation of the other.