An actuator line method for performance prediction of HAWTs at urban flow conditions: A case study of rooftop wind turbines

Blade-resolved numerical modeling of wind turbines at complex flow conditions are resource expensive due to large computational domains and extra-fine grid requirements. The Actuator Line Method (ALM) can significantly boost the simulation speed, providing acceptable accuracy and flow details. This study investigates the performance of NREL Phase VI wind turbine mounted over a high-rise building at nine different locations, providing practical illustrations of complicated flow situations. To demonstrate the superior capabilities of this method compared to the actuator disk model, two hub-heights are considered for mounting the wind turbine. Results showed that the power coefficient of the turbines with higher hub-height are close to the corresponding bare wind turbine. However, up to 52 % reduction was observed for the low hub-heights. Furthermore, variations of the bending moment experienced by the turbine's blade in a complete revolution are presented, which is a crucial factor affecting the fatigue life and structural stability of the wind turbine. Eventually, more in-depth discussions on the time-evolution of rotor performance at various locations are presented by illustrating the spanwise distributions of Angle-of-Attack histogram and its PSD diagram for the blade-1 of the wind turbine.