The Effect of Different Swell and Wind-Sea Proportions on the Transformation of Bimodal Spectral Waves over Slopes

In the laboratory experiment, 1:25 scaled models are constructed to investigate the effect of different swell and wind-sea proportions on the wave transformation. The source of the wave spectrum is related to the wave conditions in the Gulf of Guinea. Swell from the westerlies and local wind-sea forms the bimodal spectral waves in the region. To better understand the transformation of bimodal spectral waves, a series of wave conditions are measured by the wave gauges in a wave flume. Based on the wave spectrum at the Bight of Benin, the wave transformation along the slopes and variations of different swell proportions are analyzed. The result of the wave height variations shows that the slope and swell proportion play a significant role in the maximum wave height, and the wave height has an upward trend with a large swell proportion. The analysis of wave nonlinearity is conducted, showing that the large swell proportion in the wave spectrum leads to a more significant nonlinearity before wave breaking. Combining the variations of wave height and wave nonlinearity, the influence of bimodal spectral waves on nearshore wave prediction, shoreline change, marine operations, and structure design is discussed.