丁坝群坝田与主流水沙交换与冲淤机理综述

丁坝群不同平面布置方案下坝田与主流间的泥沙交换和地形变化是长江口深水航道回淤机理及减淤措施研究的重要内容,但以往研究不多。坝田与主流的泥沙交换及地形变化与紊流结构及时均流场有关,即与坝田-主流主界面混合层的大尺度相干结构和坝田内时均大尺度环流有关。在出水丁坝和淹没丁坝情况下坝田与主流的质量交换系数变化不大,约为0. 02左右。坝田不存在悬沙的平衡剖面(Rouse分布),悬沙和底沙均存在指向坝田的净输沙。坝田淤积达到准平衡状态需要5～6 a,但基本上在前2 a就达到了平衡。

View of mechanism of water and sediment exchange and sedimentation in groyne fields

The sediment exchange between groynes and mainstream and topographic change in the groyne fields under different plane layout schemes of engineering work are important issues of the siltation mechanism and sedimentation reduction measures of the deep water navigational channel in the Yangtze estuary.However,there was not much research related to it in the past.The sediment exchange between the groynes and the mainstream and the topographic change are related to the turbulent structure and the time-averaged flow field,that is,the large-scale coherent structure of the mix layer between groynes and the mainstream interface,and the time-averaged large-scale circulation in the groyne fields.In the case of unsubmerged and submerged groynes,the mass exchange coefficient between the groynes and mainstream has little change,about 0.02.There is no equilibrium profile(Rouse distribution)of suspended sediment in the groyne fields.Both suspended and bottom sediments have net sediment transport to the groyne fields.It needs about 5~6 years to reach the quasi-equilibrium state for sedimentation in the groyne fields,but it was basically completed in the first two years.