Development and assessment of an actuator volume method in rotating frame for predicting the flow-field of horizontal-axis wind turbines

Abstract

The prediction of the unsteady flow-field in horizontal-axis wind turbines using blade-resolved CFD simulations is challenging and computationally demanding. The simulations become more affordable when using a representation of the blades based on the generalized actuator disc concept; however, the projection of the computed forces in the computational domain introduces additional mesh parameters and requires codes that impact the computation time in unstructured solvers and parallel computing. In this work, a new approach to model the effects of the rotating blades using source terms and a sliding mesh technique is proposed. The developed framework also includes the tower and nacelle. The force distributions are obtained using an in-house code, which incorporates Buhl’s correction, three-dimensional effects, and tip and hub loss corrections. The validation was performed against blade-resolved simulations and experimental data at three tip-speed ratios. At design conditions, both models are in good agreement in terms of velocity deficit and angle of attack, being underestimated at off-design conditions. The local effects of the actuator volumes, the induction region, and the near-wake have been analysed in detail. This new approach is flexible, robust, and provides good accuracy, whereas the computational cost is considerably lower than high-fidelity simulations.