| Dynamic inflow models originally developed for rotorcraft applications were modified for calculation of the aerodynamic loads on wind turbine rotors. The dynamic inflow models used in this study include the simple Pitt and Peters model, the generalized dynamic wake (GDW) model and a newly developed annular section version of Pitt and Peters (P&P) model. The annular section model divides the rotor plane into ring-shaped sections and applies the Pitt and Peters model to each section separately.; The dynamic inflow models were compared with the blade element and momentum (BEM) model and field measurement data from the Tjæreborg Turbine in Denmark that were published by The Netherlands Energy Research Foundation. It was shown that the computer models predicted similar results in the calculation of rotor power.; The wake skew angle of the GDW model was modified to add directional sensitivity to the model in both the vertical and horizontal directions. This enabled the model to perform correctly with any wake skew angle.; The time constant for the changes of induced velocity was reviewed for wind turbine rotor application. The time constant was estimated from the measurement data on the Tjæreborg Turbine. However, the field measurement data could not conclusively support the prediction on the time constant, because only an insufficient number of reliable field measurement data were available.; The dynamic inflow models predicted the blade loads far better than the BEM model during yawed operations. Even when the wind condition was steady, the yaw error induced dynamic effects on the blade load and significant dynamic inflow effects. Both the annular section model and the original P&P model predicted the variation of the blade load well. However, only the GDW model predicted the 3P components of the variation in the blade flap bending moment.; The dynamic stall effect was found to have limited influence in the tested cases, because of the large size of the test turbine and its associated long time scale of load fluctuation due to the yaw error.; The dynamic inflow models experienced instability at very low wind speeds during the transition between the windmill state and propeller state. |
