黄河口泥沙输运三维数值模拟Ⅰ--黄河口切变锋

采用三维数学模型研究黄河口泥沙输运过程,并利用实测资料对模型进行了检验。数值模拟结果揭示了黄河口切变锋的时空运动过程及其对河口泥沙传输的作用。黄河口切变锋在涨、落潮时段存在两种不同的形态,分别历时2小时左右。切变锋在浅水区域产生,向深水区移动,经历2小时左右消失,它的产生是由于近岸区域与10 m深线以外区域的潮汐相位差所导致。切变锋对河口泥沙的向海传输有重要的阻隔作用,导致河口泥沙集中在切变锋的向岸一侧随落潮流向北侧传输,在涨潮时河口向海排沙量降低,少量泥沙随涨潮流沿岸向南传输。长期的地貌演化表明切变锋对河口的淤积和侵蚀分区有重要的控制作用,导致河口泥沙在其向岸一侧沉积,是长时间尺度的河口地貌演化对短时间尺度河口沉积动力过程的重要响应。

3-D simulation of the suspended sediment transport in the Yellow River mouth Ⅰ: Shear front off the Yellow River mouth

A 3-D numerical model was used to simulate the suspended sediment transport in the Yellow River mouth and verified by the in-situ measurements.The temporal-spatial variation of the shear front was revealed from the numerical results,as well as its effects on the suspended sediment transport.Two patterns of the shear front,each of which lasts for 2 hours,were identified at the flood and ebb tide phases,respectively.The results suggested that the shear front be generated in the shallow area,then moved seaward and finally disappeared 2 hours later.It seemed that the generation of the shear front was resulted from the phase leading of the tides in the shallow area to that in the deep area by about 2 hours.It was interestingly indicated that the shear front acted as a barrage to the seaward transport of the suspended sediment,retaining the river sediment transport inside the shear front along the northward ebb current.The bathymetric data indicated that a deposition zone was formed in the landward side of the shear front together with erosion zone in its seaward side,which can be regarded as an important geomorphological response of the shear front to the long-term geomorphological evolution of the Yellow River mouth.