Numerical research on the interaction of multi-directional random waves with an offshore wind turbine foundation

Real sea waves are multi-directional, but most studies on wave–structure interaction have focused on unidirectional waves. In this study, a coupled model between a potential flow solver and OpenFOAM wave basin is adopted to investigate multi-directional wave loads on an offshore wind turbine foundation. The coupled model is extended to multi-directional wave states based on the single summation method combined with the JONSWAP spectra. The numerical results are validated against the experimentally obtained values. Multi-directional waves are short-crested, the elevations are random in the wave field, and the wave pressures induced on the two sides of the cylinder are not symmetric about the principal wave direction, leading to a non-zero transverse force. In addition, the effects of wave directionality and relative ratio of foundation diameter and wavelength on wave loads are analysed. For multi-directional waves, the effects of wave directionality on transverse wave force are more sensitive than those on normal force. Wave run-up on the up-wave side increases as the directional spreading parameter decreases. In addition, wave directionality plays a complex role in the wave run-up load induced on the back side, which is found to be controlled by the relative ratio of the cylinder diameter and wavelength.