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潮汐汊道系统地貌演化的数值模拟研究
Process-based modeling of tidal inlet morphodynamics
投稿时间:2009-11-30  修订日期:2010-07-19
DOI:
中文关键词:  潮汐汊道  沉积动力过程  地貌均衡态  海岸系统演变  数值模拟
英文关键词:tidal inlets  sediment dynamic processes  morphological equilibrium  coastal system evolution  numerical modeling
基金项目:国家自然科学基金项目(面上项目,重点项目,重大项目)
作者单位邮编
谢东风 浙江省水利河口研究院 310020
高抒* 南京大学海岸与海岛开发教育部重点实验室 210093
潘存鸿 浙江省水利河口研究院 
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中文摘要:
      以过程模拟方法再现了潮流作用为主导的潮汐汊道系统演变过程.在初始状态海底平坦、汊道系统平面形态概化为矩形、底质粒度均一,忽略沿岸漂沙和径流水沙输入等条件下,根据水动力连续方程和动量方程、Engelund-Hansen沉积物输运公式和输沙连续方程建立了潮汐汊道系统演变的平面二维模型.模拟结果显示,潮汐汊道系统在潮流作用下可以达到地貌均衡态,其时间尺度为数年.由于水动力、沉积物输运和海底地形变化三者之间存在的负反馈机制,地貌演变的速率早期较快,后期逐渐减慢.潮汐汊道独特的水动力特征,即辐聚的涨潮流场与自由射流的落潮流场,是其地貌形成演变的主要机制.随着潮汐汊道地貌演变,口门水道的涨潮流速逐渐减小,历时有所增加,涨潮优势逐渐削弱,模拟结果表明,纳潮盆地多潮流通道系统的形成可分为两个阶段,第一阶段涨潮三角洲逐渐形成、淤浅,第二阶段涨潮三角洲被逐渐分割,其间发育潮流通道,通道内水深逐渐加深.
英文摘要:
      The morphodynamic evolution of an idealized inlet system is investigated using a 2-D depth-averaged process-based model, incorporating the hydrodynamic equations, Englund-Hansen’s sediment transport formula and the mass conservation equation. The model is given a fixed geometry, impermeable boundaries and uniform sediment grain size, and driven by shore-parallel tidal currents. The results show that the model reproduces major elements of the inlet system, e.g., the evolution of flood / ebb tidal deltas and tidal channels. Equilibrium is reached after several years, with the residual transport gradually decreasing and eventually diminishing. The modeled minimum cross-sectional entrance area of the tidal inlet system is comparable with that calculated with the statistical P-A relationship for tidal inlets along the East China Sea coast. The morphological evolution of the inlet system is controlled by a negative feedback between hydrodynamics, sediment transport and bathymetric changes. The unique flow field of the inlet system, i.e. a jet during the ebb and a radial inflow during the flood, is responsible for the hydrodynamic setting. The evolution rates decrease exponentially with time: the system develops rapidly at an early stage while it slows down at later stages. Temporal changes in hydrodynamics occur in the system; for example, the flood velocity decreases while its duration increases, which weakens the flood domination patterns. The formation of the multi-channel system in the tidal basin is associated with two stages; at the first stage the flood delta is formed and the water depth is reduced, and at the second stage the flood is dissected by a number of tidal channels in which the water depth increases in response to tidal scour.
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