长江口动量系数分布特征研究

基于长江口1996年3月和9月共23个测点实测水流资料,计算了动量系数的时空变化,并应用线性回归法,计算了特征时间段内的平均动量系数,获得了长江口动量系数时空分布的基本特征:时间上,涨潮大于落潮,洪季大于枯季,而大、中、小潮则依次递增;空间上,自口外向口内,北支呈逐渐增大,而南支呈先增大后减小、口门附近最大的基本特征.由动量系数分析了潮流的摩阻特性,为数值模拟合理选取曼宁系数提供参考.

Characteristics of temporal and spatial distribution of momentum coefficients for the Yangtze River estuary

Based on the field data of velocity profile observed at 23 measuring points distributed over the Yangtze River estuary in March and September,1996,the momentum coefficients are calculated and their distribution characteristics are obtained through statistical calculations. For different typical time intervals and different places in the Yangtze River estuary,the results of linear regression show that the momentum coefficients are larger for flood than forebb,and for flood season than for dry sea son,that they increase from spring tide,mean tide to neap tide on temporal distribution,and that they increase from the out side of the month to inside the month for the North Branch,and increase at first and then decrease from outside the month to inside the month for the South Branch,the maximum value appearing near the month where riverflow crosses tide on spatial distribution Through analysis,the feature of frictional resistance in the motion of tide is better understood,and an easy approach is provided for choosing the Manning coefficient for numerical simulation of plane 2-D tidal current.