The effects of oblique waves on the hydrodynamic characteristics of horizontal axis tidal current turbine

Abstract

Horizontal axis tidal current turbine (HATCT), as an effective device for obtaining tidal current energy, has received widespread attention and research. The currents and oblique waves in the ocean can evolve into complex flow fields and greatly affect the performance of HATCT, which is rarely studied, so it is necessary to explore the hydrodynamic characteristics of the HATCT under tidal currents and oblique waves. In this study, a wave-current interaction model was developed and combined with the Blade Element Momentum theory, a numerical model for calculating the hydrodynamic characteristics of the HATCT under oblique waves was established and verified. Compared to the computational fluid dynamics method, the numerical method’s computational efficiency has increased by about 869 times. After extensive calculations, the hydrodynamic characteristics of the HATCT were analyzed. Under different wave angles, the main fluctuation frequency of the power coefficient (CP) or thrust coefficient (CT) is equal to the wave encounter frequency, and the mean values of the CP or CT are almost unchanged. The multimodal phenomenon in the frequency domain of the blade CP or CT is affected by the composite frequencies of rotor rotation frequencies and wave encounter frequencies. The beat frequency phenomenon in the CP or CT is caused by the difference between the rotor rotation frequencies and wave encounter frequencies. The similarity exists in the CP or CT under the symmetrical wave angles.