  Wind turbine wakes negatively impact downwind turbines in wind farms reducing
their global efficiency. The reduction of wake-turbine interactions by
actuating control on yaw angles and induction factors is an active area of
research. In this study, the capability of spanwise-periodic wind turbine
arrays with tilted rotors to reduce negative turbine-wakes interaction is
investigated by means of large-eddy simulations. It is shown that by means of
rotor tilt it is possible to replace turbine far wakes with high-speed streaks
where the streamwise velocity exceeds the freestream velocity at hub height.
Considering three aligned arrays of wind turbines, it is found that the global
power extracted from the wind can be increased by tilting rotors of upwind
turbine arrays similarly to what already known for the case of a single row of
aligned turbines. It is further shown that global tilt-induced power gains can
be significantly increased by operating the tilted turbines at higher induction
rates. Power gains can be further increased by increasing the ratio of the
rotor diameters and turbine spacing to the boundary layer thickness. All these
findings are consistent with those of previous studies where streamwise streaks
were artificially forced by means of arrays of wall-mounted roughness elements
in order to control canonical boundary layers for drag-reduction purposes.
