Wake characterization of coupled configurations of vertical axis wind turbines using Large Eddy Simulation

Large Eddy Simulations (LES) of three different coupled configurations of Vertical Axis Wind Turbines (VAWT) are reported for two values of Tip Speed Ratio (TSR). A few studies are currently available on the wake features of isolated VAWTs, while detailed understanding of wake interaction between VAWTs is still limited, both from experiments and computations. A better insight would be very useful, since recent field tests suggested that interaction between VAWTs in array configurations is potentially beneficial, improving performance, compared to isolated turbines. It is shown here that mutual vortex interaction between wakes of coupled VAWTs is weak, while blockage effects play an important role in making available an increased momentum flux downstream. Such effects are more obvious at higher TSRs, corresponding to a larger dynamic solidity of the overall system. This result suggests that arranging turbines in staggered wind farms configurations - relative to the typical wind direction at a particular site - is beneficial in increasing the momentum flux available to rows of turbines located downstream.