Analysis and modeling of wave-current interaction

The main task of this study focuses on studying the effect of wave-current interaction on currents, storm surge and inundation as well as effects of depth-induced wave breaking, wind field and current on waves by using numerical models. The results show that it is important to incorporate the wave-current interaction effect into coastal circulation, storm surge and inundation models. At the same time, it should consider effects of depth-induced wave breaking, wind field, currents and sea surface elevation in prediction of waves. Specially, we found that: (1) Depth-induced wave breaking plays an important role in wave field in shallow water areas and resolution may also impact the wave field structure. (2) The asymmetric structure of the wind induced wave field is created not only by the asymmetric structure of the hurricane wind field, but also by the variations in the translation speed or non-zero accelerations, of a particular hurricane. With an increasing translation speed, the significant wave height (SWH) in the front-right quadrant of the wave field increases. The results further indicate that when the translation speed reaches and passes an intrinsic critical value, the SWH in the front-right quadrant begins to decrease, while increasing in the rear-right quadrant. However, the total contribution of the hurricane translation speed to the asymmetric structure of the wave field also depends on the intensity of the hurricane. As the intensity of the hurricane wind field increases, the influence of the translation speed on the asymmetric structure of the wave field is found to decrease. Most hurricane wind models are parametric and can only generate symmetric hurricanes and consider no any background wind fields, however, actual hurricanes in nature are not symmetric and contain environmental wind field effects. Thus, to more properly model the hurricane induced wave field, it is important to consider the asymmetric structure of the hurricane wind field, the changes in the hurricane translation time history, and the incorporation background wind field into hurricane wind field. (3) For SWH, it will be decreased when waves propagate in the following current direction. On the other hand, current will increase the SWH when waves propagate countercurrent direction. The effect of current on wave propagation is relative complex. The dominating mechanism affecting wave propagation direction is current (Gulf Stream) induced refraction. Depending on wind direction, it may trap some local generated waves or reflect some wave energy to open ocean. All of these mechanisms may change wave propagation direction when waves cross Gulf Stream. Therefore the change of wave propagation direction after crossing Gulf Stream depends not only on refraction, but also on others. (4) It is important to introduce wave-current effects into any storm surge and inundation prediction modeling system. Specially, the consideration of wave-induced wind stress, bottom shear stress, and 3-D radiation stress in storm surge and inundation modeling can significantly improve the correctness of the prediction.