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根据2015年1月7日至14日在长江口南槽中段主槽内获得的流速和悬沙观测资料,运用机制分解法分析了从大潮到小潮连续变化过程中南槽中段的水沙输运机制,通过小波分析方法探讨了悬沙浓度和流速的周期性对悬沙输运的影响。研究结果表明:(1)在一个大小潮周期过程中各潮周期的单宽净输水以向海为主,斯托克斯余流和欧拉余流的强度由大潮到小潮呈减小趋势;(2)各潮周期的单宽净输沙以向陆为主,与净输水方向相反,输沙强度从大潮至小潮呈现“小-大-小”的变化特征,该特征的产生与潮泵效应输沙的剧烈潮周期变化有关,平流输沙、潮泵效应输沙与垂向净环流输沙项是影响潮周期净输沙的主要成分;(3)小波分析表明,悬沙浓度和流速具有多个时间周期的变化,它们与水位的联合作用导致瞬时输沙率具有2个明显的时间周期变化。
According to the data of velocity and suspended sediment observed in the main channel of the middle section of the south channel of the Yangtze River estuary from January 7 to January 14, 2015, the mechanism of sediment transport in the middle section of the south channel was analyzed by mechanism decomposition The effects of the suspended sediment concentration and the periodicity of the velocity on the suspended sediment transport were discussed by means of wavelet analysis. The results show that: (1) The net single-net water transport in each tidal cycle is mainly seaward in a tidal cycle, and the intensity of the Stokes residual current and the Eurasian residual current decrease from tidal tide to small tide ; (2) The single-width net sediment transport in each tidal cycle is dominated by landward and opposite to the net water transport, and the change of sediment-carrying intensity from “tidal tide to tidal tide” is “small-large-small” (3) The wavelet analysis shows that the suspended sediment transport is the main component of net sediment transport in the tidal cycle. (3) Sediment concentration and velocity have many time periods, and their combination with water level lead to two obvious time-cycle changes of instantaneous sediment transport rate.