| Natural water circulation is a common phenomenon, in which its waters flow field, suspended material transport, the evolution of topography, the near-shore environment, the growth of organisms have an important impact, which caused the concern of many scholars, they had made researches on its formation, development and characteristics.This paper chose the sea near the island of Zhoushan Liuheng as a research area, based on existing topographic data, combined with the measured data of northeast coastal waters of Liuheng, made a preliminary analysis on Liuheng circulation near the shore. FLOW module of Delft-3D software was used to calculate the 3D tidal current of Liuheng, a good model in the verification based on the combination of the measured results of the analysis of the Liuheng coastal circulation features.Measured results show that, caused by the small island with a mutation in the tangential topography there existed obvious horizontal circulation, while the clockwise circulation of flood tide, ebb tide was counterclockwise. The more obvious areas of underwater terrain mutation, circulation phenomenon is more obvious, the intensity of spring tide circulation greater than the neap tide about jet stream, while the slack flow of neap tidal circulation time longer than the spring tide. In addition, jet stream times in the A section near the bottom slope break belt, and slack times in the near-shore waters, had obvious flat circulation, especially in the spring tide period. Regional vertical circulation is not obvious.Mathematical model results that:near slope break that caused by the small island and near shore formed a obvious circulation phenomenon, they would form, develop and disappear with the change of hydrodynamic force in a tidal circle. The location of circulation were kept at slope in jet stream, while in slack flow, the time would last about 0.5-2 hours, usually formed in shallow water side of the generation, dying in the deep water side,it affected areas was about 130-700m; the circulation direction from the flood tide to ebb tide changed from clockwise to counterclockwise; neap tide moments of jet velocity is relatively small, slack flow duration is relatively long circulation time, and a larger sphere of influence. Mathematical modeling results also show that slack flow of time, especially the flood of slack time, near the slope break flat circulation phenomena are obvious. Vertical circulation of water is not obvious.Overall, the trend of the measured data analysis and numerical simulation of 3D circulation obtained results are consistent, the paper reflects the circulation phenomenon of Zhoushan Liuheng coastal successfully. |
