Investigation of dynamic stall in actuator line and surface models for VAWTs

This work aims to better model the aerodynamic behaviour of vertical axis wind turbines or VAWTs by focusing on the complex phenomenon of dynamic stall, which arises when a blade recurrently and quickly undergoes large changes of angle of attack. This analysis is done in the frames of an actuator line and an actuator cylinder model coupled with a Large Eddy Simulation code and validated in view of a high fidelity vortex-particle mesh method. The results reveal that actuator line and cylinder models provide good agreement between each other in terms of forces even if some small differences logically appear in the velocity fields. Taking the model of dynamic stall into account by far increases the power for low TSRs. A more refined dynamic stall model is then implemented and proves to increase the power of the VAWT. At last, the VAWTs are simulated with an actuator line model and an actuator cylinder model with the dynamic stall and a turbulent inflow. The latter allow both models to get closer.