A general numerical model for rotor aerodynamics based on added mass force

Abstract

When wind turbines operate in complex atmospheric environments, the flow fields around their blades are complex and unsteady. To capture the lag characteristics of induced velocity when the dynamic environment of a rotor changes, this study further modified the equilibrium wake model using the blade element momentum and acceleration potential theories. In addition, a novel expression for the added mass force m A = 128/75 ρ R 3 was derived. Consequently, a numerical aerodynamics model of a rotor with an added mass force was developed. The model was used to calculate the aerodynamic load of a 5 MW wind turbine under steady wind, turbulence, gust, wind direction change, and rapid pitching. The results demonstrated that the numerical model with added mass force could reflect the rotor aerodynamic performance more accurately than its counterpart. The fluctuation amplitudes of the flapwise and edgewise bending moments of the blade root were smaller than those from the equilibrium wake model. The overshoot in loading, which was caused by the added mass force during pitching, could not be ignored. The research results were compared with experimental data from the National Renewable Energy Laboratory. It was found that the proposed model provided a new strategy for calculating the added mass force and predicted rotor aerodynamic loads more accurately than the model without added mass force.