黄河口地貌形态演变过程数值模拟

Numerical Simulation of Geomorphic Evolution Process in the Yellow River Estuary

由于黄河口来水来沙量大、变化频繁,黄河河口呈现形态多样和多变的特征。采用数值模拟再现这些特征可以揭示河口地貌形成机理和演化过程。采用计算模拟方法对黄河口动力地貌特征演变过程进行了数值模拟,再现了黄河口的2种地貌形态(双槽单浅滩型和单槽双浅滩型)。模拟采用水深平均水平二维水动力模型、泥沙输运模型以及与地形演变方程相结合的耦合模型。对耦合模型的求解采用了能够捕捉间断解的高精度的WENO差分格式。对黄河口地形演变过程纵向剖面、横向剖面和平面形态的计算结果与实际测量结果进行了比较,讨论了黄河来水来沙、潮流幅值变化对不同地貌形态之间相互转化的影响,并考虑了河口两岸淤长(动边界)对地形计算结果的影响。计算结果表明,可以实现对黄河口地貌演变的模拟预报,且模拟演变趋势与实际观测趋势大致一致,为今后模拟黄河口地貌特征的演变提供计算模型和算例参考。

Because the incoming water and sediment from the Yellow River are large in volume and change frequently,the geomorphic form in the Yellow River estuary is diverse and variable. By using numerical simulation to reproduce geomorphic features,the formation mechanism and evolution process of the geomorphology in the estuary can be revealed. In this paper,the dynamic geomorphic features and evolution processes in the Yellow River estuary are simulated by means of computer simulation method and two types of geomorphic forms（ a double-channel and single-lobe type and a double-lobe and single-channel type） are reproduced. The horizontal two-dimensional hydrodynamic model and the sediment transport model,which are coupled with the topographic evolution equation,are used for the simulation. For the solution of the topographic evolution equation,the high precision WENO difference scheme which can capture discontinuous solutions is applied. The calculated and measured results of the topographic evolution processes in the Yellow River estuary（ including longitudinal sections,cross sections and flat forms） are compared. The influences of the incoming water and sediment from the Yellow River and the tidal current amplitude variations on the reciprocal transformation between the two types of geomorphic forms are discussed.The effects of the silting-up at the estuarine banks（ moving boundary） on the results of topographic calculations are also considered. It has been shown that the forecast trends simulated for the geomorphic evolution in the Yellow River estuary are basically consistent with the actual observations.