Waveform and Turbulence Influence on Wake Morphology Within a Floating Windfarm

The aerodynamic and hydrodynamic forces experienced by floating wind turbines introduce complex dynamics between the turbine and platform orientation, wave conditions, and wake behavior. To maximize the performance of these farms it is necessary to understand the influence each of these factors has on the net behavior. This work conducts a series of particle image-velocimetry (PIV) measurements within a scaled floating windfarm to analyze the coupling behind wind, waves, and wakes. Experiments take place in the Portland State University wind-wave tunnel, equipped with a wave generator, damper, and active grid. Twelve semisubmersible, tri-floater turbines with a rotor diameter of 15 cm are arranged into a farm of four rows. Multiple spanwise-vertical PIV planes are taken downstream of the center turbine in the third row to capture a developed wake within the farm and observe the impact waves have on its morphology. Encoded DC motors in the nacelle of the turbines are used to set the tip speed by varying the resistive load. Multiple waveforms, turbulence intensities, and Reynolds numbers are considered. Mean flow fields and Reynolds stresses are presented, both as ensemble and phase average quantities, to highlight any wave dependence. Resulting data characterize a scaled floating wind farm. Such data is expected to be useful for model development and subsequent optimization strategies for full-size farms.