A new class of actuator surface models for wind turbines

Xiaolei Yang, Fotis Sotiropoulos

Published 2017-01-12Version 1

Actuator line model has been widely employed in wind turbine simulations. However, the standard actuator line model does not include a model for the turbine nacelle which can significantly impact turbine wake characteristics as shown in the literature (e.g. Kang, Yang and Sotiropoulos, Journal of Fluid Mechanics 744 (2014): 376-403; Viola et al., Journal of Fluid Mechanics 750 (2014): R1; Foti et al., Physical Review Fluids 1 (2016), 044407). Another disadvantage of the standard actuator line model is that more geometrical features of turbine blades cannot be resolved on a finer mesh. To alleviate these disadvantages of the standard model, we develop a new class of actuator surface models for turbine blades and nacelle to take into account more geometrical details of turbine blades and include the effect of turbine nacelle. The actuator surface model for nacelle is evaluated by simulating the flow over periodically placed nacelles. Both the actuator surface simulation and the wall-resolved large-eddy simulation are carried out. The comparison shows that the actuator surface model is able to give acceptable results especially at far wake locations on a very coarse mesh. The capability of the actuator surface model in predicting turbine wakes is assessed by simulating the flow over the MEXICO (Model experiments in Controlled Conditions) turbine and the hydrokinetic turbine of Kang, Yang and Sotiropoulos (Journal of Fluid Mechanics 744 (2014): 376-403). Comparisons of the computed results with measurements show that the proposed actuator surface model is able to predict the tip vortices, turbulence statistics and meandering of turbine wake with good accuracy.