Hydrodynamic study of wave-current coupling in Zhoushan under typhoon condition

Abstract The hydrodynamic characteristics of the Zhoushan sea area under the influence of Typhoon 2106 In-fa were numerically simulated using the FVCOM-SWAVE wave-current coupling model. The simulation results indicate that the astronomical tidal current field in this region exhibits distinct semi-diurnal tidal characteristics. The dominant water flow pattern in the Zhoushan sea area is a reciprocating motion from the northwest to the southeast, with spring tide velocities reaching up to 2.5m/s, which can facilitate the formation of localized torrents. The superimposition of Typhoon In-fa and astronomical tides led to a significant storm surge threat along the Zhoushan coastline. Narrow waterways within the island group experienced particularly severe increases in water levels, with surges of up to 138cm. The east side of Zhoushan faced significant impacts from the extreme waves generated by the typhoon, while the west side was somewhat protected by the island barrier, resulting in a relatively smaller overall wave impact. In the periods before and after typhoon landfall, Hangzhou Bay witnessed substantial changes in its flow field, characterized by vorticity formation and increased velocities. The interior of Zhoushan is mainly affected by the tidal current, but because of the difference of the gradient of the flow field, it is easy to form local vortex. This research offers valuable hydrodynamic environmental insights, serving as a crucial reference for disaster prevention and mitigation strategies in the Zhoushan sea area.