杭州湾北部潮流深槽区细颗粒物质输运与再悬浮过程  

Fine-grained sediment transport and resuspension process in a tidal channel of the northern Hangzhou Bay in China

作　　者：杨旸[1] 高抒[1] 汪亚平[1] 

机构地区：[1]南京大学海岸与海岛开发教育部重点实验室,江苏南京210093

出　　处：《海洋学报》2008年第2期92-101,共10页

基　　金：国家自然科学基金重点资助项目(40231010)

摘　　要：于2005年5月大潮期间在杭州湾北部潮流深槽区的4个站位进行潮周期观测,获得了流速、悬沙等数据,并对其进行了分析,计算了水沙通量和再悬浮通量。分析结果表明,该深槽区涨潮流速大于落潮流速,涨潮历时小于落潮历时,潮差自湾口向湾内方向增大;悬沙的组分以粉砂为主,分选较差,偏态以负偏为主,这些特征与底质一致;深槽中部和东部的悬沙沿岸线向湾内方向输运;深槽西部和东部外侧的悬沙输运方向与余流方向一致,分别向湾内和南部输运;除转流和流速加速初期外,垂线流速分布符合Kármán-Prandtl模型,摩阻流速与垂线平均流速变化趋势一致。计算得到的表观粗糙长度在涨落潮时段的水流加速或减速阶段都呈增大趋势,且数值较大,这难以把它简单地归结为床面形态的作用,表观粗糙长度的变化趋势可能是高悬沙浓度和浓度成层性共同作用的结果,但对这一假说的验证还有待于进一步的现场观测和机制分析。计算所得的再悬浮发生的周期性与实测悬沙浓度的周期性相符,而且最大悬沙浓度的出现滞后于最大再悬浮通量,说明再悬浮作用对水层中悬沙浓度的变化具有重要影响。Tidal cycle measurements of current velocities and suspended sediment concentrations were carried out at four stations in a tidal channel （Jinshan Channel） in the northern Hangzhou Bay in China during a spring tide period in May 2005, together with water and seabed sediment sampling. Data sets were analyzed to obtain suspended sediment transport rates and resuspension fluxes. The results show that the tidal channel is dominated at the flood stage, with a tidal range increasing from the baymouth towards the bayhead areas. The suspended sediment consists mainly of silts, poorly sorted and mostly negatively skewed, being consistent with the bed matter. In the central part of the channel, the net sediment transport direction which directs towards the bayhead differs from the residual current direction. In the other parts, the two directions are consistent, being directed towards the south in the east and towards the bayhead in the west. Except for the slack water stage, the vertical distribution patterns of current speed can be described by the Karman-Prandtl model, with the calculated shear velocity having a similar trend to the vertically averaged current velocity. At most stations, the calculated apparent roughness length shows a trend of increase from the beginning of flow acceleration to the end of flow deceleration during both flood and ebb phases of the tide, with extremely large values. Such a pattern cannot be explained by form drag alone; it may be result from a combined effect of high suspended sediment concentration and stratification due to vertical concentration differences within the water column. Further observations and analyses of the associated mechanisms are required to examine this hypothesis. It is shown that the occurrence of resuspension and the measured suspended sediment concentrations have the same periodicity and the maximum concentration lags behind the maximum resuspension flux, indicating that the resuspension process represents an important factor controlling the concentration with

关 键 词：悬沙输运 再悬浮 边界层过程 潮流深槽 杭州湾 

分 类 号：P731.23[天文地球—海洋科学]