| Yangshan Deep-water Harbor(YDH)is located at the junction of the Changjiang Estuary and Hangzhou Bay.It is consisted of northern-island chain,southern-island chain and a deep channel between the two chains.The hydrodynamics in the YDH is complicate due to its geometry.YDH is frequently impacted by storm tides and waves caused by typhoon.In this study,based on the F VCOM hydrodynamic model and the FVCOM-SWAVE wave model,a tide-surge-wave coupling numerical model was used to study the hydrodynamics and the impacts of typhoon in YDH.The influence of the main controlling factors of the storm tide on the storm surge during typhoon was quantized.Taking super typhoon "Chan-hom" as an example,the measured data of wind speed,wind direction,water level,current and significant wave height were analyzed.The characteristics of currents and residual currents after the construction of the YDH were numerically examined.The total water level,total storm surge and significant wave height during storm tide were studied.The contributions of the wind,air pressure and wave on the storm surge were compared.The model adopts a high-resolution,large-area grid,and after verificating of the measured data,it can accurately simulate the impact of typhoon on the hydrodynamic of YDH.The main conclusions are as follows:(1)The current speed is higher in the deep channel than that in the south and in the north of the islands.The peak currents and eddies occur at the entrance of the deep channel.The peak current speed is up to 2.88 ms-1 at the surface level during the spring flood tides.The current speed is higher in the south of the islands than that in the north.The current speed is higher during flood time than ebb time in the west of deep channel.During the flood slack time,the vertical current circulation occurs,with northward surface current and southward bottom current.During the ebb time,the vertical current circulation occurs,with southward surface current and northward bottom current at the deep channel.(2)In the deep channel,the M2 tidal ellipses are rectilinear and the directions of the major axis are along the channel controlled by the coastlines.The major axis of M2 tidal ellipses decreases from the surface to the bottom,and the variations of the directions is less than 10°.In the west of channel,the surface/bottom tidal ellipses rotated clockwise/anti-clockwise.The maximum residual current appeared in the narrow channel.The residual current decreases along with the increase of water depth.The direction of the residual current is mainly seaward,except in the deep channel.The separate of residual currents occurs in the deep channel.The location of the stagnation point moves eastward after the construction of the YDH.(3)The highest water level occurred later than the peak surge.The highest water level occurred at the high tide.The peak surge appears at the low tide.YDH has the similar surge during typhoon "Chan-hom" as the area is small.The peak surge occurs at the north coast of the northern-island chain,due to the backwater by the chain.The flow field in YDH is slightly southward compared with that of astronomical tide.The highest significant wave height occurred later than the highest water level,but at the same time with the highest wind speed.Due to the blocking of the north-south island chain,the significant wave height in the east of the island chain is significantly higher than that in the west.(4)The winds contributed 87.1%of the peak surge of storm,followed by the pressure-induced surge(23.7%).The third one,which contributed about 14.4%of the peak surge of storm,is wave-induced surge.The surge in the narrow channel was lower than that in the other areas of the YDH.The peak surge induced by wind occurred first,followed by the wave-induced and the air pressure-induced surges.The wave-induced peak surge appeared at the highest water level.The wind-induced peak surge appeared simultaneously with the peak surge of storm. |
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