Analysis of Power Performance and Wake Interference in a Three-Turbine Tandem Array of Offshore Wind Turbines

This study investigates multiple-wake interactions and downstream power losses in a heterogeneous tandem array comprising DTU 10-MW and NREL 5-MW offshore wind turbines. TurbSim is used to generate turbulent inflow fields, and a three-turbine tandem array is simulated in FAST. Farm using the Dynamic Wake Meandering model. Seven turbine configurations and 57 simulation scenarios are considered to systematically examine the effects of streamwise spacing, inflow turbulence intensity, turbine-type combination, and turbine-type arrangement on power output and wake evolution. The results show that increasing the streamwise spacing generally improves the power output and wake power retention ratios of the intermediate and downstream turbines. Compared with uniform inflow, turbulent inflow with a prescribed turbulence intensity of 15% generally enhances momentum exchange across the wake shear layers, accelerates wake recovery, and reduces downstream power losses, although its effect on total array power depends on the turbine configuration. Turbine-type arrangement affects downstream performance by changing the spatial extent of the wake generated by the intermediate turbine and its vertical overlap with the rotor-swept area of the downstream turbine. At a streamwise spacing of 5Dref and a turbulence intensity of 15%, placing the NREL 5-MW turbine at the intermediate position and the DTU 10-MW turbine downstream results in a downstream wake power retention ratio of 53.2%. Reversing their positions reduces this ratio to 31.9%. Nevertheless, the corresponding total array powers differ by only 0.3 MW because the power outputs are redistributed between the intermediate and downstream turbines. These findings demonstrate that streamwise spacing, inflow conditions, and turbine-type arrangement should be considered jointly when evaluating the wake recovery and power performance of heterogeneous offshore wind-turbine arrays.