感潮河段潮流分离方法研究

Study of detiding method in tidal reach

分析了Green和Gauss两种常用基函数的特点及适用范围,得出了在感潮河段利用基函数法进行潮流分离的关键是节点个数及节点位置的选取.根据潮流分离中流速拟合误差随节点个数增加达到某一数值会趋于稳定这一规律,提出了用于节点个数选取的阈值法,并根据流场的流速缓急及梯度变化提出了用于节点位置确定的梯度算法.实验以长江口徐六泾附近的感潮河段为研究区域,采用传统的基函数法和提出的基于阈值法及梯度算法的组合方法对该水域8个走航断面及5条固定垂线的大、中、小潮3个时段的声学多普勒流速剖面仪(ADCP)数据进行了潮流分离.结果表明:提出方法的流场拟合精度明显优于传统方法,且内符合精度和外符合精度基本一致,表明该方法构建的流场具有较好的短时段外推功能.

This paper analyses the characteristics and application of Green and Gauss functions and concludes that the number and the position of nodes is the key of detiding.Threshold method was proposed to determine the number of nodes based on fitting error and gradient algorithm was put forward to determine the position of nodes based on the changes of flow field.The tidal reach in the vicinity of Xuliujing of the Yangtze River estuary was taken as the study area.Traditional Candela method and the combination of threshold method and gradient algorithm proposed were adopted to separate the mean flow and tidal current from vessel-mounted ADCP data of three periods of spring,middle and neap tide in the eight sections of the water.The results show that the accuracies of proposed method is much better than that of traditional method.In addition,the interpolation and extrapolation accuracies for the same period are consistent,which indicates that the interpolation scheme proposed in this paper is valid and effectiveness in short-time extrapolation.