On Wind-Wave Misalignment, Directional Spreading and Wave Loads

Abstract

Causes of wind-wave misalignment, the difference between wind and mean wave direction, are investigated for stationary and non-stationary situations using numerical modeling. This includes the effects of upwind fetch restrictions, refraction, choice of source terms and integration time step on wind-wave misalignment are illustrated. A statistical analysis is performed to quantify wind-wave misalignment as a function of wind speed and significant wave height. In addition, the effect of spectral partitioning in separate wind sea and swell systems on the statistics of wind-wave misalignment is illustrated. Apart from the differences in mean direction, attention is given to the associated directional spreading. Implications for the design of offshore structures and the movements of moored ships are discussed.