Unsteady aerodynamic prediction for dynamic stall of wind turbine airfoils with the reduced order modeling

A surrogate based reduced order method is developed for the prediction of the unsteady dynamic loading of wind turbine airfoils under dynamic stall situation. S809 airfoil undergoing sinusoidal pitch oscillation at different reduced frequencies, mean angles of attack and pitch oscillation amplitudes at Re = 106 are simulated by the CFD method. Then, the Kriging function is selected to establish the unsteady and nonlinear aerodynamic model with training cases generated by the CFD method. The results reveal an encouraging agreement between the CFD simulations and the reduced order model predictions. Furthermore, Ohio State University measurement data and Leishman-Beddoes model predictions for test cases are also included. Because CFD has good accuracy simulation for flow field around the airfoil under dynamic stall condition, the reduced order model can more effectively predict the airfoil nonlinear hysteretic behavior than L-B model. In addition, the reduced order method has relatively less computational cost compared with the CFD method. Therefore, it would be useful in engineering conditioning for aero-elastic analysis and design optimization of wind turbines.