The hydrodynamics of Beilun Estuary, Guangxi, China is under the controls of multiple factors such as runoff,tide,wave,longshore currents and wind drag,which make the flow field much complex. In this paper,the characteristics of tidal currents and mechanisms of the formation of Low Frequency Current are investigated withlong time series of current profile data at 2 observation stations,SI and S2. Methods of mathematical statistics,harmonic analysis of tidal current and digital filter are used in the analysis. The results show that the tidal current in Beilun Estuary is mainly irregular diurnal tide. During the investigation, flow velocities of peak flood and peak ebb were 39,83cm/s at station SI ,and 52,44cm/s at station S2. The residual current velocity gradually decreased from surface layer to bottom layer,and the velocity at station S1 was mainly 5 ~10cm/s and that at S2 was mainly 0 ~5 cm/s. At station S1 ,the residual current mainly flowed to S - SW. At station S2 ,the residual current of surface and middle layers mainly flowed to NNE - ENE, while it flowed to W at the bottom layer. Wind-stress was the main forcing agent for the residual current at the surface and near surface layers in surveying area. Meanwhile, the residual current was strongly affected by alongshore current, and the residual current at station S1 was also influenced by the river runoff. The contribution of residual tidal current on the residual current is marginally.%北仑河口水动力状况复杂,受入海径流、潮汐、波浪、沿岸流、风应力等多种因子的共同影响.对北仑河口S1、S2站长序列的海流剖面资料进行数学统计、潮流调和分析和数字滤波,探讨其潮流特征和余流形成机制.分析结果表明:北仑河口潮流性质主要为不规则全日潮流；观测期间S1站实测涨、落潮最大流速分别为39、83 cm/s,S2站分别为52、44 cm/s.研究海域余流流速从表层往底层逐渐减小,其中S1站余流流速主要介于5～10cm/s之间,流向集中在S- SW向,S2站主要介于0～5cm/s之间,表、中层以NNE - ENE向为主,底层以偏W向为主.风应力是调查区表层与近表层余流形成的主导因素；西向沿岸流对调查区的余流也有较明显的作用；径流对调查区的S1站有一定的影响,但对S2站影响很小；潮致余流对调查区的余流贡献较小.
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