The objective of this paper is to numerically investigate the effect of the atmospheric boundary layer on the aerodynamic performance and loads of the novel dual-rotor wind turbine (DRWT) proposed by Rosenberg et al. Assuming that the turbine operates in isolation, numerical analyses are carried out for two atmospheric stability conditions: (1) neutral, and (2) stable. Comparisons are drawn with the corresponding analyses of a comparable conventional single-rotor wind turbine (SRWT) to assess changes in: (a) aerodynamic efficiency, and (b) dynamic loads on the turbines. The results show that the DRWT improves isolated turbine performance even when atmospheric boundary layer effects are considered. It is also found that the DRWT enhances wake mixing when background turbulence due to the atmospheric boundary layer is moderately high. This has implications on wind plant performance when multiple turbines are placed one behind the other. No significant increase in aerodynamic loads is observed in the DRWT design. In fact, the out-of-plane blade root moment of the main rotor is reduced in the DRWT. Spectral analyses show peaks in unsteady loads at the rotor blade passing frequency and its harmonics for both the primary and secondary rotors. Loads at other (combination) frequencies are observed in the secondary rotor.
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