潮流不对称现象是近岸潮波运动的基本特征之一，为了研究潮流不对称对推移质泥沙长期净输运的作用机制，首先在往复流情况下对 Bagnold 推移质输沙率公式(1966)由于不包含起动流速所可能导致的误差进行理论分析，进而由统计学中的“偏度”的概念出发，推导了河口潮流不对称与推移质输沙之间的定量关系。研究认为，虽然Bagnold推移质输沙率公式不包含泥沙起动流速，但是只要泥沙起动流速和最大流速的比值在一定范围内，则在理论上公式的计算误差是可以接受的。由偏度结合 Bagnold 公式导出了潮流不对称与推移质输沙之间的关系，表明推移质泥沙的长期净输运不仅与余流有关，而且与不同分潮组合之间、余流与分潮之间的相互作用紧密相关。该关系还给出了一个由潮流调和常数估算河口推移质输沙的简便方法。经对比，从潮流不对称出发估算推移质输沙与直接采用推移质输沙率公式结果一致。%Tidal current asymmetry is one of the fundamental characters of nearshore tidal wave. In order to inves-tigate the influence of tidal current asymmetry on net long-term bed sediment transport, the error of bed-load com-putation that was induced by excluding incipient velocity was studied, while using the Bangnold equation in recti-linear currents. Furthermore, a quantitative relationship between the tidal asymmetry and the bed-load transport in estuaries was deduced based on the concept of skewness. It is shown that the result calculated by the Bagnold for-mula without incipient velocity is approximately accurate in theory, while the ratio of the incipient velocity of bed-load to the maximum velocity is smaller than a certain value. The relationship derived from the Bagnold equa-tion and tidal asymmetry shows that the long-term net transport of bed-load is affected by the combination of dif-ferent tidal constituents as well as that of residual current and tidal constituents. The relationship also gives a con-venient method to estimate the bed-load transport by harmonic constants of tidal currents. The results obtained through the relationship well match those directly obtained through the Bagnold equation.
展开▼
