A wind tunnel study on multi-scale wake dynamics of a floating wind turbine under individual and coupled heave and pitch motions

Abstract

Floating offshore wind turbines are a core technology for exploiting deep-sea wind energy. However, the complex influence of platform motion on wake dynamics remains a critical bottleneck limiting wind farm performance. This study systematically investigated the modulation mechanisms of heave and pitch motions, both in isolation and in combination, on the aerodynamic wake of a floating offshore wind turbine using wind tunnel testing. The results indicate that the impact of platform motion on time-averaged properties was localized, being dominated and homogenized by high background turbulence in the far field. Nevertheless, this influence exhibited duality in coherent structures: motion disrupted initial vortex structures in the near field, reducing the spatial correlation from 0.74 to approximately 0.63; however, in the far field, it increased the long-range correlation from 0.20 to 0.36 by exciting large-scale wake meandering. Modal analysis further revealed the origin of this multi-scale effect. In coupled motion, heave dominated the first wake mode (macroscopic dynamics), while pitch governed higher-order modes (fine-scale internal structures). This mechanism of scale-specific roles, where different motion modes operate at distinct scales, provides a novel framework for understanding wake evolution in floating wind turbines under complex motions and has important implications for the optimal design and control of future wind farms.