Influence of thrust coefficient on the wake of a wind turbine: A numerical and analytical study

In this study, large-eddy simulations (LES) are used to analyze how variations in the thrust coefficient influence the wake of an actuator disk. In a neutrally-stratified turbulent boundary layer, the flow through a stand-alone actuator disk is simulated on flat terrain with two different aerodynamic roughness lengths, using a thrust coefficient varying from 0.4 to 0.9 in 0.1 increments. The simulation results show that the thrust-coefficient variation leads to considerable differences in the wake velocity deficit and added turbulence intensity distributions up to downwind distances of around 12 disk diameters. Moreover, the resulting dataset is used to evaluate the performance of several analytical and empirical wake models for different thrust coefficients. Emphasis is placed on the models for the mean wake velocity deficit, near-wake length, and added turbulence intensity. In general, the models that incorporate physically-based approaches within their framework have an advantage over empirical models derived from a given dataset. The former yields predictions for the wake velocity deficit and near-wake length that are more accurate and robust to the thrust-coefficient variation. For the added turbulence intensity, the predictions of some commonly used models are compared with the LES data, and recommendations for their range of applicability are given. • Large-eddy simulations of actuator disks of various thrust coefficients are presented. • Systematic analysis of thrust coefficient effect on actuator disk wake is performed. • The accuracy of wake models for wake mean and turbulence quantities are evaluated. • Relations derived from wake physics are robust to variation in the thrust coefficient. • Frandsen model reasonably predicts far-wake added turbulence intensity for all cases.