灌河口潮汐不对称数值模拟研究

建立灌河口平面二维潮流数字模型,并在灌河口口门至陈家港河段沿程布置5个采样点和3个横向断面,通过对各采样点一个月数值模拟结果进行调和分析,得出灌河口M2分潮及其主要倍潮的基本特征,然后利用潮位-流速关系图及通过对动量方程中各项的统计计算,研究了灌河口潮波运动的基本动力平衡、M2的主要倍潮的产生机制及其对潮汐不对称现象的影响。研究认为:灌河口潮汐潮流均属正规半日潮型。M4、M6分潮对于灌河口潮波变形有着重要的影响,M8分潮除在浅滩处外对潮汐不对称的影响很小。在深槽处M4分潮导致最大落(涨)潮流速减小(增大),最大涨(落)潮流速与最高(低)潮位之间的相位差增大。M6分潮的影响与M4基本一致,但其作用明显小于M4分潮。在浅滩处M4分潮导致最大涨落潮流速均大于M2分潮的值,M6和M8分潮使最大涨落潮流速均出现在高潮位附近,但M6、M8使最大涨潮流速减小,而使最大落潮流速增大。外海边界处倍潮波的传入对于口门附近的潮汐不对称有一定影响。M4和M6分潮导致灌河口的潮汐不对称表现为涨潮主导型,潮波运动主要受到压强梯度力、非线性对流和底摩擦力,三者与局地惯性力构成灌河口的基本动力平衡,摩擦力并不是最重要的作用力。

A numerical study of tidal asymmetry in Guanhe River estuary

Simulations of tides are carried out using a vertically integrated 2D numerical model in Guanhe River estuary. Simulated tidal elevation and tidal current at five sites along the channel and three cross sections are harmonically analyzed. The distributions of M2 and its overtides of M4, M6 and M8 are then examined. The main momentum balance, generation of overtides of M2 and its contributions to tidal asymmetry are studied based on stage velocity diagrams and comparisons of the terms in u momentum equation. It shows that the Guanhe River estuary is semi diurnal. M4 and M6 make significant contributions to tidal distortion, while M8 has minor effects almost everywhere except on some shoals. In the main channel, M4 and M6 increase (decrease) the maximum flood (ebb) current, while M6 plays a secondary role. In the side channel, the maximum ebb current and flood current are both larger than that of M2 when M4 is added. M6 and M8 make the maximum flood and ebb current velocity occur almost at the time of the highest water. M6 and M8 decease the maximum flood current velocity and increase the maximum ebb current velocity. The M4 open boundary forcing plays an un negligible role especially in the low part of the estuary. Flood dominance occurs in the Guanhe River estuary due to M4 and M6. The barotropic pressure gradient, the advective inertia and the bottom friction are the three main forces, and the Guanghe River estuary is not frictionally dominated.