【作者】 诸裕良；

【导师】 严恺； 严以新；

【作者基本信息】 河海大学 ， 港口、海岸及近海工程， 2003， 博士

【摘要】 本文首先针对辐射状沙脊群现有的文献及实测资料，初步分析研究了南黄海辐射沙脊群海域地貌和动力特征，以及动力与地貌的关系。基于过程分裂法及垂向坐标伸缩变换，外模式采用改进型双步全隐有限差分DSI法，内模式采用欧拉—拉格朗日公式，改进了三维垂向隐式格式，成功地建立了南黄海辐射状沙脊群海域三维全隐格式潮流数学模型。通过对辐射沙脊群海域平面及立面动力特征的研究，基本探明了南黄海辐射沙脊群形成发育和维持的水动力机制，以及其不对称分布格局与动力因素的内在联系。 平面潮流椭圆、水质点迹线、潮流流速特征研究表明，辐射状沙脊群海域潮流具有明显的定向往复流形式，平均潮流流速一般为0.6～1.0m／s，满足形成潮流沙脊的水动力条件。通过对潮波波面传播过程及潮波能流率研究表明，辐射沙脊群海域为南部太平洋前进潮波和北部旋转潮波所控制，两潮波系统在弶港外海辐聚辐散，形成大潮差区的特点。另外还研究了辐射沙脊群海域的余流及余流量的分布，发现在潮流沙脊两侧存在平面余环流，余环流将有利于泥沙在脊顶沉积，与潮流沙脊的维持发育密切相关。 研究主要潮流通道及沙脊横剖面的涡度场。首次发现，在潮涨潮落过程中，深槽中及沙脊两侧均存在一组方向相反、不对称余涡度场(余环流场)，横向余环流的存在将有利于沙脊两侧的泥沙均向沙脊顶运动和堆积，是潮流沙脊的形成和维持重要动力因素。应用Hulscher沙波及沙脊增长模式，通过对该海域斯托克斯数及底部阻力参数的计算首次发现，南黄海辐射沙脊群海域在概化古地形和现代辐射状沙脊群水下地形情况下，其斯托克斯数及底部阻力参数均满足形成潮流沙脊的条件。故在有充分泥沙供应的条件下，辐射沙脊群海域必然会形成潮流沙脊，并且辐射沙脊群在现代水动力条件下仍将维持。 各种动力特征平面分布规律研究表明，辐射沙脊群南北沙脊不对称分布的格局是潮流沙脊对潮流往复流性质的强弱分布、潮波能流率大小分布、含沙量的平面分布规律及斯托克斯数的大小分布的动力响应。更多还原

【Abstract】 First.upon the former research work and field measurements in the radial sandbanks area, the characteristics of geomorphology, hydromechanics and the relationship between them are preliminarily analysed. Though adopting the σ-coordinate transformation in the control equations and mode-splitting technique, the external mode (surface gravity waves) is solved by the improved double-sweep-implicit finite difference method; the internal mode (internal gravity waves) untilizes the Eulerian-Lagrangian method, which improves the implicit-difference scheme for the vertical direction. The newly developed 3D numerical tidal model with implicit scheme has been successfully applied in the radial sandbanks area. Through studing the plane and vertical hydromechanical characteristics in the radial sandbanks area, the mechanisms of the formation, maintenance and asymmetrical distribution of the radial sandbanks are understood.It’s well known that the directional to-and-fro movement and strong tidal current are the necessary dynamic conditions for the formation of tidal current sandbanks. The tidal current in the radial sandbanks area apparently has directional to-and-fro movement, which can be observed not only from tidal ellipses, but also from water particle traces. The calculated distribution of tidal velocity in this area shows that the average velocity is around 0.6 to 1.0 m/s. It has been proven that, from the propagation process of the tidal waves and wave energy rates, the whole radial sandbanks area is controlled by the progressive tidal wave in the south and the rotational standing tidal wave in the north. These two waves merge at Qianggang and induce a large tidal range. The distributions of the residual flow and the residual discharge from the numerical model show that the residual circulation flows around the sandbanks contribute significantly to the deposition at the peak of sandbank, and closely related to the sandbank development.The existence of the asymmetrical residual transverse circulation flows in pair is discovered in the residual vorticity field along the passage and sandbank cross section. The transverse residual circulation flow is favorable to sediment’s moving to the peak of sandbank and the development and maintenance of sandbank. Using the Hulscher model of the formation of sand waves and sandbanks, under the ancient bathymetry, or under the modern bathymetry, the Stokes number of the tidal flow and resistance parameter in the radial sandbanks satisfy the conditions for the formation of sandbanks. The research demonstrates that the dynamic flow conditions result in the development of tidal current sandbank. The radial sandbanks and it’s asymmetrical distributions will still maintain in the future.It has been proven that the differences of magnitude and distribution of tidal currents, wave energy rate, suspended sediment concentration and the Stokes number result in aasymmetrical distribution of sandbanks between the north and south. The sandbank surface area and length in the north are lager than those in the south, but its cross section area is less than that in the north.更多还原