Frontogenesis, mixing, and stratification in estuarine channels with curvature
Frontogenesis, mixing, and stratification in estuarine channels with curvature
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DOI：
10.1175/jpo-d-21-0298.1
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发表时间：
2022-03
影响因子：
3.5
通讯作者：
Tong Bo;D. Ralston
中科院分区：
文献类型：
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作者：
Tong Bo;D. Ralston
采用理想化数值模拟方法，研究了河道曲率对河口层化和混合的影响。与直槽河口相比，弯曲河口的层化减少，潮能耗散增加。我们采用了垂直盐度方差预算，以量化的分层应变和混合的影响。二次环流由于渠道曲率被发现通过横向应变和增强垂直混合的影响在弯曲的渠道分层。在弯曲顶点的上游和下游，分别出现交替的正、负侧向应变，对应于正、反向的曲率次级环流。弯曲通道中的垂直混合局部增强，最大混合位于弯曲顶点的上游。在弯曲顶点上游的内岸附近，由于二次流和分层的相互作用，产生弯曲尺度的底部盐度锋。底层锋的剪切混合，而不是二次环流的翻转混合，是破坏层结的主要机制。航道曲率也会导致阻力增加，使用辛普森数与此增加的阻力系数可以与更广泛的河口参数空间的曲率分层的减少。
Idealized numerical simulations were conducted to investigate the influence of channel curvature on estuarine stratification and mixing. Stratification is decreased and tidal energy dissipation is increased in sinuous estuaries compared to straight channel estuaries. We applied a vertical salinity variance budget to quantify the influence of straining and mixing on stratification. Secondary circulation due to the channel curvature is found to affect stratification in sinuous channels through both lateral straining and enhanced vertical mixing. Alternating negative and positive lateral straining occur in meanders upstream and downstream of the bend apex respectively, corresponding to the normal and reversed secondary circulation with curvature. The vertical mixing is locally enhanced in curved channels with the maximum mixing located upstream of the bend apex. Bend-scale bottom salinity fronts are generated near the inner bank upstream of the bend apex as a result of interaction between the secondary flow and stratification. Shear mixing at bottom fronts, instead of overturning mixing by the secondary circulation, provides the dominant mechanism for destruction of stratification. Channel curvature can also lead to increased drag, and using a Simpson number with this increased drag coefficient can relate the decrease in stratification with curvature to the broader estuarine parameter space.