长江河口河槽水沙特性及其输移机制研究

Transport mechanism and characteristics of water and suspended sediment in channels of the Changjiang Estuary

基于2007年1、7月长江口大潮实测流速及悬沙量资料,运用数据统计和机制分解法分析各河槽水沙输移特性,结果表明:枯季优势流小于洪季,枯季北支、南支北侧、北港中下段、南槽南边滩为涨潮优势,其他河槽为落潮优势,洪季北槽口外为涨潮优势,其他河槽为落潮优势;悬沙输移主要驱动力为欧拉余流、潮泵效应、垂向环流和斯托克斯余流,欧拉余流在平流输沙中占主导地位,潮泵效应在潮流输沙中占主导地位,欧拉余流指向海,垂向环流和斯托克斯余流指向陆,潮泵效应除北港口外、南槽口外随季节变化外其余河槽指向海;不同汊道各输沙项的贡献随径流与潮汐潮流的相对重要性而变化。

Based on observation data of current velocity and suspended sediment concentration in the Changjiang Estuary in January and July 2007,the transport mechanism and characteristics of water and suspended sediment are analyzed by using the method of statistical data and decomposition mechanism. The results show that preferential flow usually in dry season is smaller than in flood season; During the dry season,the rising tide dominated in North Branch（ NB）,north of South Branch（ SB）,the middle and lower of North Channel（ NC） and the south beach of South Passage（ SP）,while the ebb tide dominated in other channels.During the flood season,the rising tide dominated in the outside of NC,while the ebb tide dominated in other channels. Analysis on the mechanisms of sediment transport reveals that Euler residual flow,tidal pumping,Stokes effect and vertical-longitudinal circulation are main forcing agents leading to residual sediment transport. Euler flow plays a vital role in the non-tidal steady advection transport,and tidal pumping plays a vital role in the tidal transport. Euler residual flow caused seaward transport,while Stokes effect and vertical-longitudinal circulation landward transport. Sediment transport due to tidal pumping varied with season in the outside of SP and NP,while seaward transport in other channels. The contribution of each sediment transport item in different channels is varied as the relative importance of the runoff,the tide and trend changing.