Enhancing wake recovery in vertical-axis wind farms through blade pitching

The present work investigates the effectiveness of blade pitch control in vertical-axis wind turbines for improved wake recovery and re-energization in a semi-infinite offshore wind farm subject to sheared inflow conditions. The study employs an Unsteady Reynolds-averaged Navier–Stokes solver in OpenFOAM, with turbines represented using the actuator line method. All turbines operate synchronously, and two fixed blade-pitch offsets are examined as test cases. The results highlight the pivotal role of the vortex system in shaping wake topology and governing kinetic energy replenishment across the wind farm. In the pitched cases, modified tip vortices substantially enhanced wake recovery by increasing the advective flux of kinetic energy, which accelerated the re-energization of the turbine wakes. As a result, downstream turbines experienced power gains of 58%–123% relative to the baseline, depending on the pitch setting, while the most upstream rotor exhibited only a minor power reduction. This translated into overall farm power-density improvements of 15% and 41% for the two pitch cases, respectively, compared to the baseline. Although only two fixed-pitch cases are examined, the optimal pitch angle to maximize farm power is an open question.