Wake-induced alteration of C p - λ characteristics and operating equilibrium in downstream wind turbines

Abstract

Wake interaction in wind farms modifies the inflow conditions for downstream turbines. However, their influence on the aerodynamic performance of individual turbines remains unclear. This study investigates how wake-added turbulence (WAT) and the disturbed inflow shift the normalised power coefficient ( $C_p$ ) and tip-speed ratio ( $\lambda$ ) using Fast.Farm. Four aligned configurations of NREL 5 MW turbines were simulated under steady inflows of 4 m/s to 25 m/s, with WAT enabled, for two inter-turbine spacings (7.5D and 10D). The results show that turbines operating within strong and wake superimposed regions exhibit higher $C_p$ and $\lambda$ values, with T3 showing a maximum $C_p$ of 0.596 at 7.5D spacing, despite reduced power compared with the upstream turbine. Increasing spacing to 10D reduced the wake-induced shift in aerodynamic operating behaviour and improved downstream power recovery, especially within the 8-12 m/s wind speed range. These findings highlight WAT’s influence on the operating equilibrium of downstream turbines.