Decoupling wind–wave–wake interactions in a fixed-bottom offshore wind turbine. (1st March 2022)

• Record Type: Journal Article
• Authors: Ferčák, Ondřej; Bossuyt, Juliaan; Ali, Naseem; Cal, Raúl Bayoán
• Is Part Of: Applied energy. Volume 309(2022)
• Publication Date: 2022-03-01
• Subjects: Turbulence -- Particle image velocimetry -- Offshore wind energy -- Offshore wind farm -- Wake recovery -- Wind–wave–wake interaction; Power (Mechanics) -- Periodicals; Energy conservation -- Periodicals; Energy conversion -- Periodicals; 621.042
• DOI: 10.1016/j.apenergy.2021.118358
• Languages: English
• ISSNs: 0306-2619

Abstract

Abstract: The interest and benefits of offshore wind energy have also brought along legitimate challenges. In the golden age of renewables, offshore wind-energy holds the most potential for growth, but the burgeoning benefits of offshore energy are also entangled in dynamics not fully understood, such as the dynamic coupling of the atmospheric boundary layer, the wind-turbine generated wake, and the surface waves. This study establishes the first experimental turbulent-interaction between the traditionally distinct fields of airflow-dynamics above the air–sea interface and the characterization of wind-turbine wakes. The study details a non-trivial experimental setup combining a wave tank, wind tunnel, and scaled fixed-bottom wind turbine. Particle image velocimetry (PIV) was performed on three successive image planes to visualize wind–wake, wind–wave, and wave–wake interaction far downstream of the turbine. The wave phase-dependent dynamics of the turbine wake on the passing ocean-wave profile and location are outlined. The velocity and stress profiles showed a horizontal wake-pumping motion along with vertical wake-lifting of the offshore turbulent wake. The data were decomposed into incremental wave-phases revealing localized and predictable velocity maxima, stress maxima, and wake modulation that is normally obscured by a time-averaged mean. The results quantified wake pumping and meandering, as well as the Reynolds stress and wave-induced phase-averaged fluctuations. There is a phase-dependent oscillation in both the horizontal (streamwise) direction, as well as a vertical displacement of the wake. The shear stress and advection terms show this imbalance along the vertical direction of the turbine. The results illustrate a more complete picture of offshore wind-energy dynamics, which have implications for insidious mechanical issues, design optimization and/or control strategies. Highlights: Novel wind–turbine wake, atmospheric boundary–layer, and ocean–wave dynamics. Experimental consideration of an offshore fixed–bottom wind turbine. Wave–phase characterization to visualize downstream wake development. Wave–induced decomposition reveals velocity and Reynolds stress dependencies. Phase dependence in horizontal and vertical turbine wake displacement.