Rotational Augmentation Disparities in the MEXICO and UAE Phase VI Experiments

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.

[1]  Daniel Micallef,et al.  Validating BEM, Direct and Inverse Free Wake Models with the MEXICO Experiment , 2010 .

[2]  P. Giguere,et al.  Design of a Tapered and Twisted Blade for the NREL Combined Experiment Rotor , 1999 .

[3]  Sven-Erik Thor,et al.  The execution of wind energy projects 1986 - 1992 between China Aerodynamics Research and Development Centre (CARDC) and The Aeronautical Research Institute of Sweden (FFA) , 1993 .

[4]  J G Schepers,et al.  The MEXICO project (Model Experiments in Controlled Conditions): The database and first results of data processing and interpretation , 2007 .

[5]  Scott Schreck,et al.  Boundary Layer State and Flow Field Structure Underlying Rotational Augmentation of Blade Aerodynamic Response , 2003 .

[6]  Scott Schreck,et al.  Low Frequency Shedding Prompted by Three-Dimensionality under Rotational Augmentation , 2010 .

[7]  Maureen Hand,et al.  Unsteady Aerodynamics Experiment Phase VI: Wind Tunnel Test Con gurations and Available Data Campaigns , 2001 .

[8]  N. B. Siccama,et al.  MEXICO Project: The Database and Results of Data Processing and Interpretation , 2009 .

[9]  Scott Schreck,et al.  Rotational augmentation of horizontal axis wind turbine blade aerodynamic response , 2002 .

[10]  Tonio Sant,et al.  Estimating the angle of attack from blade pressure measurements on the NREL phase VI rotor using a free wake vortex model: Axial conditions , 2006 .

[11]  Michael Robinson,et al.  Aerodynamic structures and processes in rotationally augmented flow fields , 2003 .

[12]  Peter T. Zell,et al.  Performance and test section flow characteristics of the National Full-Scale Aerodynamics Complex 80- by 120-Foot Wind Tunnel , 1989 .