Large eddy simulation of helical- and straight-bladed vertical axis wind turbines in the atmospheric boundary layer flows

In this study, the turbulent wake flows behind helical- and straight-bladed VAWTs operating in the atmospheric boundary layer (ABL) are investigated using large-eddy simulation (LES). In the LES model, the aerodynamic forces induced by the turbine blades are applied to the flow field utilizing the actuator line model. The interaction between the VAWTs and the ABL flow is modeled using a concurrent precursor simulation method. In particular, a precursor LES is used to obtain the fully developed ABL turbulence, which provides the inflow condition for the main LES in which the VAWTs are modeled. A straight-bladed VAWT is used as the benchmark case, and several helical-bladed VAWTs with different blade twist angles are considered to explore the effect of the blade helicity on the wake flow characteristics. Based on the simulation results, systematic statistical analyses are performed to characterize the differences in the turbulent wake flows generated by the helical- and straight-shaped blades and their effects on wind energy harvesting.