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引用本文:易雨君,唐彩红,张尚弘.波浪条件下刚性植被茎干紊流对沉积物再悬浮的促进作用.湖泊科学,2020,32(6):1827-1836. DOI:10.18307/2020.0622
YI Yujun,TANG Caihong,ZHANG Shanghong.Effect of stem-generated turbulence on sediment resuspension within rigid vegetation canopies in waves. J. Lake Sci.2020,32(6):1827-1836. DOI:10.18307/2020.0622
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波浪条件下刚性植被茎干紊流对沉积物再悬浮的促进作用
易雨君1, 唐彩红1, 张尚弘2
1.北京师范大学水环境模拟国家重点实验室, 北京师范大学环境学院, 北京 100875;2.华北电力大学水利与水电工程学院, 北京 102206
摘要:
浅水湖泊沉积物再悬浮过程促进了沉积物内源性物质的释放,造成湖泊水体内源污染,加剧湖泊水质污染与生态恶化.开展刚性植被不同分布格局下的沉积物再悬浮水槽试验,能为浅水草型湖泊、滨海湿地等水环境治理与生态修复提供理论参考.本研究通过开展实验室波浪水槽试验,检验了3种直径12种密度的刚性模型植被对波浪扰动白洋淀沉积物再悬浮的影响,通过测定不同植被情景不同波浪条件下的瞬时速度和沉积物再悬浮浓度,详细阐述了植被产生的紊动能对沉积物再悬浮临界状态的影响,构建并验证了沉积物再悬浮植被紊流模型,预测了沉积物再悬浮的临界速度,为湿地生态恢复与保护提供参考.结果表明:1)植被的存在能有效增加近床面的紊动能;2)紊动能是控制沉积物再悬浮的关键性因素;3)沉积物再悬浮的临界波速与植被的固相体积分数相关.
关键词:  刚性植被  沉积物再悬浮  波浪  紊动能  临界阈值  浅水湖泊
DOI:10.18307/2020.0622
分类号:
基金项目:国家重点研发计划项目(2018YFC0407403)、国家自然科学基金项目(51722901)和北京市自然科学基金项目(JQ19034)联合资助.
Effect of stem-generated turbulence on sediment resuspension within rigid vegetation canopies in waves
YI Yujun1, TANG Caihong1, ZHANG Shanghong2
1.State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, P. R. China;2.School of Water Resources and Hydropower Engineering, North China Electric Power University, Beijing 102206, P. R. China
Abstract:
Sediment resuspension in shallow lakes promotes the nutrients release, which leads to the internal pollution, degrading the water quality and lake ecology. This research aims to study the impact of rigid vegetation on wave-driven sediment resuspension through wave flume experiments. It could provide a theoretical reference for environmental management and ecological restoration of shallow lakes and coastal wetlands. Vegetation canopies were constructed by rigid cylinders considering three diameters and 12 vegetation densities. The near-bed instantaneous velocity was measured within vegetation canopies and under different wave conditions by a Nortek Vectrino at sampling rate of 200 Hz. Suspended sediment concentrations were measured using an optical backscatter with frequency of 20 Hz. The vegetation-generated turbulence was positively linear with the root mean square of wave velocity. This vegetated turbulence increased with an increasing ratio (Aw/S) of wave excursion (Aw) to stem spacing (S) when Aw/S>1, and was similar with bare bed case when Aw/S<1. The concentration of sediment resuspension increased with growing solid volume fraction. The critical state of resuspension was initiated when the suspended sediment concentration exceeded the background level. Higher solid volume fraction generated higher turbulence, which promoted a small critical wave velocity. A vegetation-generated turbulence model for sediment resuspension was proposed and validated using the measured turbulence in the model canopy. Therefore, we confirmed that the magnitude of stem-generated turbulence is a function of solid volume fraction. This model proved the key role of turbulent kinetic energy to control the initial sediment resuspension. Based on this, a threshold model of critical velocity for sediment resuspension was proposed and validated. It could predict the critical near-bed wave velocity for sediment resuspension within rigid vegetation canopy or sheath with diameters of 0.32 cm to 1.2 cm. The applicable particle size was limited to 85-280 μm.
Key words:  Rigid vegetation  sediment resuspension  wave  turbulence  velocity threshold  shallow lakes
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