Study On The Influencing Dynamic Factors And Their Mechanism Of Tidal Current Limit In The Yangtze River

The water in the lower reaches of the Yangtze River is driven by the combined force of the upper runoff and the lower tidal effect,its movement is ever-changing.The tidal current limit is a considerable performance in the dynamic change,which is effected by several factors and in a continuous state of movement,showing a lot of complex features in different kinds of hydrological conditions.On the basis of predecessors,this article has worked with measured terrain data,built a 2D tidal numerical model of the lower Yangtze river(from DaTong station to the estuary)with CJK-3D water environment numerical model in unstructured mesh.The model verification was so fine that it demonstrated a precise simulation of the real movementChapter two&three has analyzed the water flow characteristics in tidal part of the Yangtze River from many aspects:water level,tidal range,raising-ebb time and tidal volume.Furthermore,it expounded the characteristic of tidal current limit by different computational outcome,especially the effect of tidal and river in different conditions.Result showed that the major range of tidal reversing limit in the river is between Nanjing and BaiMaosha river month around.The flood season change of river is more effective to the dividing line than tidal variety.When runoff is increasing in the same rate,velocity of its movement to river month is slower and slower.Vice versa,its speed to upper reach is slowed down when the tidal range increased.In the fourth chapter,taking the Jiangjiang waterway as an example,the effect of the terrain on the distribution of the tidal current in the straight river is analyzed.The results show that the tidal-river rate in the shoal is smaller than that of the deep groove in the same section.In the upper reaches of the tidal current boundary,the tidal current limit moving-velocity in the deep trough will be faster than that of the shallow trough.In the upstrean part of tidal river,the difference between the tidal-river rate in the shallow trough is big,and the same index of dowstream part is much lower,the upstream and downstream is divided by the tidal current limit.