How does the rotational direction of an upwind turbine affect its downwind neighbour?

Abstract Wind-turbine blades rotate in clockwise direction looking downstream on the rotor. During daytime conditions of atmospheric boundary layer, rotational has no influence turbine wakes. In stably stratified occurring during night, inflow is often characterized by a veering describing wind change with height Northern Hemisphere. A changing interacting rotor impacts its wake characteristics (wake elongation, width and deflection). We investigate impact performance (streamwise velocity for power, turbulence kinetic energy loading) downwind considering four possible combinations directions two 5 MW NREL rotors means large-eddy simulations. counterclockwise rotating upwind results 4.1% increase averaged at comparison to common case rotors, 4.5%. This streamwise accompanied 3.7% energy. The difference (+4.8% cumulative power both turbines, if rotates counterclockwise) from dependent amplification or weakening spanwise vertical components, which result superposition rotation.