| 三沙湾夏季底边界层动力过程及悬沙输运特征 |
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| 引用本文： | 齐昱恺,涂俊彪,于俊杰,范代读.三沙湾夏季底边界层动力过程及悬沙输运特征[J].海洋科学,2021,45(6):1-12. |
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| 作者姓名： | 齐昱恺 涂俊彪 于俊杰 范代读 |
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| 作者单位： | 同济大学,同济大学,中国地质调查局南京地质调查中心,同济大学 |
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| 基金项目： | 国家自然科学基金项目（面上项目，重点项目，重大项目）；中国地质调查局项目 |
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| 摘 要： | 基于2018年8月福建三沙湾湾内外共两个定点站位的船基和座底三脚架观测数据，研究了三沙湾底边界动力过程及悬沙输运特征。结果表明，三沙湾湾内湾外两个站位均表现出涨落潮历时相近但涨落潮流速明显不对称的现象，即湾内涨潮流速大于落潮流速，湾外则相反。湾内水体受淡水输入影响较大，表现出落潮期间显著的温盐层化，而涨潮期间水体混合良好；湾外水体受淡水影响不明显，表现为水体温度主导的层化。通过对底边界层动力过程的分析表明，湾内（距底0.75 m）、湾外（距底0.50 m）站位底边界层的平均摩阻流速分别是0.016 m/s、0.013 m/s，且两个站位拖曳系数基本相等（2.03×10-3），表明在相同流速下湾内站位的底部切应力更大，近底沉积物再悬浮和搬运相对湾外站位更为显著。因此观测期间悬沙浓度最大值出现在湾内站位，为109 mg/L，且悬沙在垂向上的分布可达上层水体；湾外站位悬沙浓度更低，并且底部悬浮泥沙仅能影响至距底5 m的水体。悬沙通量机制分解结果表明，三沙湾夏季的潮周期单宽悬沙从湾外向湾内方向净输运，湾内站位向湾内方向净输运74.88 g/(m·s)，平流输沙占主导作用，贡献率41.7%；湾外站位向湾内方向净输运10.57 g/(m·s)，主要受平流输沙和垂向净环流的控制，贡献率94.9%
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| 关 键 词： | 三沙湾 底边界层 摩阻流速 悬沙输运 悬沙机制分解 |
| 收稿时间： | 2021/2/27 0:00:00 |
| 修稿时间： | 2021/4/6 0:00:00 |
Hydrodynamic processes of the bottom boundary layer and suspended sediment transport in the Sansha Bay in summer |
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| QI Yu-kai,TU Jun-biao,YU Jun-jie,FAN Dai-du.Hydrodynamic processes of the bottom boundary layer and suspended sediment transport in the Sansha Bay in summer[J].Marine Sciences,2021,45(6):1-12. |
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| Authors: | QI Yu-kai TU Jun-biao YU Jun-jie FAN Dai-du |
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| Institution: | Tongji University,Tongji University,Nanjing Geological Survey Center of China Geological Survey,Tongji University |
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| Abstract: | A detailed field observation on hydrodynamic processes of the bottom boundary layer and suspended sediment transport mechanisms was conducted at two sites inside and outside the Sansha Bay in August 2018. The results show that the two sites in the inner bay and the outer bay show similar ebb and flood duration but asymmetry on ebb and flood velocity. The flood velocity of the inner bay site is larger than ebb velocity, whereas the outer bay site is opposite. The water column in the bay is greatly affected by fresh water, showing significant temperature and salinity stratification during ebb tide, while the water mixes well during flood tide. The water outside the bay is thermally stratified and not significantly affected by fresh water. The analysis of the hydrodynamic processes of the bottom boundary layer show that the average friction velocity of the bottom boundary layer at the site in the bay (0.75 m above the bottom) and outside the bay (0.50 m above the bottom) are 0.016 m/s and 0.013 m/s, respectively. The drag coefficients of the two sites are basically the same (2.03×10-3) at different heights. This indicates that the bottom shear stress inside the bay is greater than that outside the bay at the same current velocity. Thus the resuspension and transport of near-bottom sediments inside the bay is more significant than those outside the bay. Therefore, during the observation period, the maximum suspended sediment concentration appeared at the site inside the bay(109 mg/L), and the vertical distribution of suspended sediment could reach to the upper layer; the suspended sediment concentration outside the bay was lower, and the suspended sediment was confined in the lower 5 meters above bottom. The results of the mechanism decomposition sediment transport indicate that during the summer time, the net suspended sediment transport was from the outer- bay to inner bay. At the inner bay, the dominant mechanism of suspended sediment transport is advection, which contributes 41.7% of the total sediment flux. As the result, the net suspended sediment transport is 74.88 g/(m·s). At the outer bay, the net suspended sediment transport is 10.57 g/(m·s) from the outer bay o to the inner bay, mainly controlled by advection and vertical net circulation with a contribution rate of 94.9%. |
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| Keywords: | Sansha Bay bottom boundary friction velocity sediment transport decomposition of suspended sediment mechanism |
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