风暴潮模拟中潮位对风拖曳力系数的影响研究

近年来,应用数值模型模拟台风引起的风暴潮运动越来越普遍,模型中对于风拖曳力系数的确定,一般都从相对风速出发,可引用的公式也较多,但这些公式很少考虑潮位变化对此系数的影响.在强潮河口、海岸海域,潮位变幅大,最高潮位甚至可达风速参考高度(10m)的近一半,如长江口和杭州湾.在数值模拟中不考虑风暴潮和天文潮共同引起的潮位变化,会造成风应力高潮时被低估、低潮时被高估的现象,从而影响风暴潮模拟的精度.为此本文对现有的风拖曳力系数加以改进,提出了考虑潮位影响的风拖曳力系数表达式,并应用于长江口、杭州湾9711号台风风暴潮的模拟中,增水模拟结果得到了明显改善,可进一步推广应用于强潮河口、海岸的风暴潮增水模拟中.

Research of the effluence of tidal level on wind drag stress coefficient in storm surge model

Storm surge model has been used widely to simulate the non-astronomical tidal set-down and set-up occurring in typhoon season. In model there are many formulas about wind stress coefficient can be used to calculate the wind drag stress on free surface. But in conventional formula only the relative wind speed is considered without considering the effluence of tide level. Actually in intensive estuarine and coastal area, the tidal range is large, even reaching half of the reference height of 10m, such as the Yangtze estuary and Hangzhou bay. So the precision of model will be reduced because the wind stress is underestimated in flood tide and be over-valuated in falling tide without considering the fluctuation of water itself. Therefore the relationship of the relative wind speed and water elevation should be considered together. A new kind of wind stress formula has been established in this paper and used to simulate the storm surge of typhoon Winnie in Yangtze Estuary and Hangzhou bay. The results are better and satisfying. The new formula can be used in the future storm surge model in intensive estuarine and coastal areas.