珠江口黏性泥沙絮凝的湍流动力机制

任杰; 张颖

doi:10.3969/j.issn.0253-4193.2019.09.010

珠江口黏性泥沙絮凝的湍流动力机制

doi: 10.3969/j.issn.0253-4193.2019.09.010

任杰^1,,
张颖¹

中山大学海洋科学学院近岸海洋科学与技术研究中心，广东广州 510275

基金项目: 国家自然科学基金（41476072）。

详细信息

作者简介:
任杰（1975—），男，四川省南部县人，副教授，博士，主要从事近岸河口动力过程研究。E-mail：renjie@mail.sysu.edu.cn

中图分类号: P731.26
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出版历程
- 收稿日期: 2018-08-10
- 修回日期: 2018-10-23
- 网络出版日期: 2021-04-21
- 刊出日期: 2019-09-25

The turbulent dynamic mechanism of flocculation of cohesive sediment in the Zhujiang River Estuary

Ren Jie^1
,,
Zhang Ying¹

Center for Coastal Ocean Science and Technology, School of Marine Sciences, Sun Yat-sen University, Guangzhou 510275, China

摘要

摘要: 本文利用2010年枯季在珠江口进行的大、中、小潮LISST剖面及底边界层观测资料，分析了磨刀门河口枯季稳定存在的絮团三峰结构，即构建絮团的基本粒子的平均粒径约为8.3～9.0 μm，小絮团为36～100 μm，大絮团大于180 μm。小潮期，盐跃层捕集的悬浮泥沙以强絮凝过程为主，大絮团含量占优；中、大潮期，平均粒径普遍增大，絮凝占优。潮内的动力变化对絮团多峰结构及形态参数的影响不明显，絮凝与解凝处于动态平衡。结合坐底三角架的湍流资料和简化的群体平衡模型(Population Balance Equation，PBE)，进一步揭示了絮团变化的湍流动力机制。高流速下的强紊动剪切力，直接导致大絮团被破坏形成小絮凝体，絮凝体平均粒径减小，反之絮凝强于解凝作用。同时，基于高斯矩积分方法求解PBE，得到的粒径分布基本与观测值吻合，说明在有较好的现场湍流与粒径观测资料的条件下，PBE包含的湍流动力机制可以用来研究黏性泥沙的絮凝过程。
- 珠江口 /
- 絮凝 /
- 湍流 /
- 群体平衡方程
Abstract: This thesis aimed to analyze the stable multimodal (3-peaked) particle size distributions (PSDs) of flocs in the Zhujiang River Estuary with the field observation data getting by LISST and the bottom boundary layer observation system during the dry season in 2010. The results show that the mean diameter of the basic building blocks of flocs, so-called primary particle, is about 8.3–9.0 μm; the mean diameter of microflocs in a range of 36–100 μm, and macroflocs have a size range of 180 μm to thousands of micrometers. In the neap tidal periods, the suspension sediment of halocline is dominated by the macroflocs with strong flocculation process; the mean diameter of flocs is increases and is controlled by flocs during the moderate and spring tide. The dynamic change of the tide has little impact on the multimodal PSDs and morphological parameters, with aggregation and breakage of the flocculation in the dynamic equilibrium. Study results further demonstrate the turbulent dynamic mechanism of flocculation by combining the turbulence data collected by the bottom tripod and the simplified Population Balance Equation (PBE). It is that, the high shear of the peak flow would enhance breakage of macroflocs to microflocs and decrease the mean diameter of flocs, on the contrary, aggregation is much stronger than breakage. It also shows that PSDs are in according with observation by solving PBE based on gaussian moment integral method. It turns out that PBE which containes the turbulent dynamic mechanism can be used to study the flocculation of cohesive sediment with turbulence and PSDs data.
- Zhujiang River Estuary /
- flocculation /
- turbulence /
- population balance equation

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图 1 磨刀门河口在珠江三河口湾中的位置（a）及2010年12月15–24日磨刀门水道水文观测站位分布（b）

Fig. 1 The Zhujiang River Estuary and research area (a) and the distribution of observation stations from December 15, 2010 to December 24, 2010 at Modaomen Estuary (b)

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图 2 灯笼山站边界层的3个观测测次时间与对应的潮型

Fig. 2 Three observations of the bottom boundary layer and corresponding tide types at Denglongshan Station

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图 3 观测期间风速风向过程曲线

Fig. 3 The time process of wind direction and speed during the observation

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图 4 M2站剖面轴向流速（a），盐度（b），体积浓度（c），絮团粒径（d）分布

图中轴向流速的正值表示涨潮，负值表示落潮

Fig. 4 The profile distribution of velocity (a), salinity (b), volume concentration (c) and diameter of flocs (d) at M2 Station

The positive (+), negative (-) values of the axial velocity represent the flood tide, ebb tide, respectively

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图 5 H1剖面的粒径分布（a, b, c）和S1剖面的粒径分布（d, e, f）（a, d为表层；b, e为中层或跃层；c, f为底层）

Fig. 5 Particle size distributions of surface (a, d), middle/halocline (b, e) and bottom (c, f) layers in H1 (a, b and c) and S1(d, e and f) profiles

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图 6 不同剪切率下的粒径分布（a）及粒径随时间演化过程（b）

图a中C₁与C₂分别表示碰撞效率与破坏频率参数，C是泥沙浓度^[32]

Fig. 6 Experimentally obtained steady-state particle size distributions with different shear rate (a) and time process of flocs evolution (b)

C₁ and C₂ represent collision efficiency and failure frequency parameters, respectively; C is the sediment concentration^[32]

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图 7 M2站观测期间的剪切率与模拟的平均粒径（a）及颗粒粒径分布（b）

Fig. 7 The time process of shear rate and simulated mean diameter of particles (a) and particle size distributions (b) at M2 Station

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表 1 观测仪器设置参数

Tab. 1 The parameters set of the observation instruments

观测方式	仪器	参数设置	测量项目
船载系统	LISST-100B	整点下放，采样频率为1 Hz	剖面泥沙粒径分布
	CTD	整点下放，采样频率为1 Hz	温、盐、深
座底观测	ADV	采样频率为64 Hz，测量间隔为5 min，采样时间为3 min，位置分别为0.25 mab、1.35 mab	单点三维高频流速、声强
	OBS	采样间隔1 min采样，平均时间为10 s，位置分别为0.4 mab、0.9 mab	单点浊度
	RBR-CTD	采样频率为1 Hz，位置为0.5 mab	温、盐、深
	PC-ADP	测量间隔为5 min，采样频率为1 Hz，每次测量180个剖面，盲区为0.10 m，位置为1.3 mab	剖面流速
注：mab表示离床面的高度，单位：m。

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表 2 特征剖面多峰结构的絮团拟合参数

Tab. 2 A summary of flocs fitting parameters for particle size distributions at typical profiles

剖面（观测时间）	层位	观测值			曲线拟合：平均粒径/μm			曲线拟合：体积浓度/μL·L^–1			曲线拟合：几何标准差
剖面（观测时间）	层位	H/m	V/μL·L^–1	D/μm	m1	m2	m3	m1	m2	m3	m1	m2	m3
H1（2010年10月15日16时）	S	1.6	47.5	47.1	8.5	36	230	4.4	30.1	21.9	1.3	1.59	1.41
	H	5.5	2 674	178.3	43	100	237	43	1 824	1 836	1.21	1.2	1.27
	B	7.2	140	71	8.6	41	230	40	67	103	1.43	1.29	1.32
H2（2010年10月15日21时）	S	1.6	46	48	8.5	36	159	4	26	18	1.05	1.24	1.68
	H	5.6	3 883	155	50	99	178	154	521	3 294	1.42	1.06	1.2
	B	6.6	95.6	55.4	8.6	37	230	40	23	33	1.38	1.78	1.35
S1（2010年10月20日17时）	S	1	623	164	8.8	49	198	9	53	600	1.17	1.59	1.17
	H	3.6	655.2	165	8.9	51	200	9	58	633	1.17	1.66	1.17
	B	7.2	697	171	8.9	49	209	9	57	725	1.17	1.58	1.17
S2（2010年10月21日4时）	S	1	898	136	8.8	48	228	31	109	1 069	1.34	1.7	1.27
	H	3.2	910	133	8.8	49	238	31	180	1 219	1.34	1.72	1.29
	B	6.5	1 332	135	8.3	50	240	29	277	1 776	1.31	1.93	1.23
注：S、H、B分别代表表层、跃层或中层、底层；V和D表示观测的总体积浓度和平均粒径；m1、m2、m3分别为3个分解模态；H表示水深。

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