长江口南港泥沙运动的水动力条件

Hydrodynamic conditions for sediment movement in South Waterway of Yangtze River Estuary

应用流体运动最小阻力原理导出了分流角发育的理论计算公式 ,并在弓形断面假定条件下 ,对不同宽度比时的分流角作了计算 ,得出了与实测值相一致的结果 ;同时还定量地证明了长江南北港、南北槽分流角发育由小到大 ,直至极限而消亡的规律 .分汊水槽试验表明推移质大多偏向支汊 ,原因是在分流口支汊一侧由于边界层脱离而“搓”出一个个旋涡以吸引底沙 .分析得知 ,从南港主槽下泄的落潮流 ,在扩散角增大处 。

A theoretical formula for calculation of the diversion angle is developed by means of the least resistance principle. The diversion angles for different river widths are calculated on the assumption of arch shaped cross section, and the calculated results are consistent with the measured data. It is verified that the diversion angle included between the North Waterway and the South Waterway develops from small to large, and then dies out. Experiments performed in a bifurcated tank demonstrate that most of the bed load moves towards the tributary, where a series of vortexes are generated due to flow deviation from boundary layers, and that, for the same reason, the ebb flow from the South Waterway of the Yangtze River Estuary will push the bed load into the South Channel due to the similar vortexes around the diversion angle included between the North Channel and the South Channel.