Abstract Surface waves significantly influence the hydro-mechanical response of tidal turbines by inducing variations in structural loading and wake dynamics. Yet, there are few comprehensive databases available for studying these physical processes. To address this gap, we carried out experimental trials on a three-bladed horizontal-axis tidal turbine in a combined wave-current flume tank, testing two wave propagation directions. Our results do not highlight any specific influence related to the direction of wave propagation. It is however shown that waves amplify load fluctuations, particularly at twice the wave frequency, when excited by sidebands of the rotation frequency. Wave-induced variations in wake width appears primarily driven by local flow perturbations due to wave orbital velocity surrounding the wake, whereas wake centroid motion is governed by the wave-generated time-varying dynamics of the rotor. The study of the frequency content of the flow reveals wave-related sidebands around both three and six times the rotational frequency. Frequency analysis of the flow reveals wave-related sidebands around both the blades passing frequency and its second harmonic. This observation is interpreted as wave-induced modulation of tip vortex positions, analogous to waves propagating along a slinky helical spring, which is confirmed by the results of an analytical tip vortices model.
Dufour et al. (Fri,) studied this question.