基于高频ADCP资料的磨刀门河口羽状流湍流动力特征

The dynamic characteristics of turbulence in the Modaomen Estuary river plume based on the ADCP data

利用1 200kHz的宽频RDI ADCP于2015年7月在磨刀门河口拦门沙前缘的浅水站和沿岸流影响的深水站进行座底观测,采样频率为1Hz,数据经滤波去噪处理,应用方差方法分析了磨刀门的羽状流湍流动力特征。结果表明,磨刀门河口水流表现出3层流结构,峰值流速出现在表层的羽状流层,深水区雷诺应力量级为10-3~10-5 m2/s2,小于拦门沙前缘的湍流脉动强度;拦门沙前缘和深水区湍流动能密度参数的范围均在0.01~0.6m2/s2左右,羽状流的湍动能比底边界层高一个数量级。拦门沙前缘羽状流的湍动能生成率量级约为10-3 W/kg,比底层大2~3个量级,且远强于深水区;垂直涡黏系数的大小约为0~0.15m2/s。总的来说,羽状流表现出层化稳定、混合强烈,以及高的湍动能生成率,为羽状流携带高浊度悬沙离岸远距离搬运提供了湍流动力条件。

This thesis aimed to analyze the dynamic characteristics of turbulence with the field observation data getting by a 1 200 kHz,broadband RDI ADCP rigidly mounted in the front of the sand bar and in the deep-water zone in the Modaomen Estuary in July 2015,with the＂variance method＂.The results show that the flow velocity presenta typical three-layer circulation structure,and high-speed velocity area appeared in the Modaomen Estuary river plume.The Reynolds stress estimated in the deep-water zone was between 10-3-10-5 m2/s2,and smaller than that in the front of sand bar.The turbulence kinetic energy density parameter was larger in the river plume than in the bottom,and the size of it in both place was between 0.01-0.6 m2/s2.In the front of the sand bar,the turbulence kinetic energy production rate was in the order of 10-3 W/kg in the river plume,2-3 orders of magnitude lager than that in the bottom and stronger than that in the deep-water zone.The vertical eddy viscosity coefficient was between 0-0.15 m2/s.In general,the river plume presents a state of stably stratified,with strongly mixed and high turbulence kinetic energy production rate,which provides a dynamical condition for the long-distance transport of high turbidity suspended sediment.