Blade Three-Dimensional Dynamic Stall Response to Wind Turbine Operating Condition

Abstract

To further reduce the cost of wind energy, future turbine designs will continue to migrate toward lighter and more flexible structures. Thus, the accuracy and reliability of aerodynamic load prediction has become a primary consideration in turbine design codes. Dynamically stalled flows routinely generated during yawed operation are powerful and potentially destructive, as well as complex and difficult to model. As a prerequisite to aerodynamics model improvements, wind turbine dynamic stall must be characterized in detail and thoroughly understood. The current study analyzed turbine blade surface pressure data and local inflow data acquired by the NREL Unsteady Aerodynamics Experiment during the NASA Ames wind tunnel experiment. Analyses identified and characterized two key dynamic stall processes, vortex initiation and vortex convection, across a broad parameter range. Results showed that both initiation and convection exhibited pronounced three-dimensional kinematics, which responded in systematic fashion to variations in wind speed, turbine yaw angle, and radial location.