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1.
生态空心块体是一种兼有调控水流与生态修复功能的工程结构物,在海堤、丁坝等近海工程中被广泛应用。通过室内水槽试验,设计多种来水来沙工况,研究生态空心块体与柔性植被共同影响下的水沙动力特性,重点探究生态空心块体内的水沙动力效应。结果表明:生态空心块体组成的坝体结构缓流效果显著,坝体内外侧水流流速分布差异明显,坝体内部的水流流速远小于外侧水流流速;生态空心块体内紊动强度、雷诺应力在空心块体上方出现拐点,空心块体内紊动强度、雷诺应力均小于外侧;近底层水流在受壁面阻水作用下产生回流,易出现小范围旋涡;由于生态空心块体内水流流速、紊动强度的减小,内部悬沙浓度由表至底逐渐增大;柔性植被的冠层部分对水流减速、促淤效果最为明显,柔性植被会减缓前后相邻侧空心块体的水流流速,增大悬沙浓度。 相似文献
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钱塘江河口细颗粒泥沙絮凝沉降特性研究 总被引：3，自引：0，他引：3
钱塘江口河口上游河流和海域来沙多为细颗粒泥沙,粘性细颗粒泥沙由于其特殊的表面电化学性质遇到强电解质海水而产生絮凝沉降,是形成河口淤积的原因之一。影响絮凝的因素很多,除了电解质,还有泥沙粒径的大小、盐度、含沙量、PH值、温度、有机质含量、矿物成分、水流速度及紊动情况等。本文通过粒度分析、静水沉降、动水沉降等各种实验手段分析钱塘江口泥沙的基本特性,找出最佳絮凝盐度以及泥沙不淤流速等值,初步探讨了细颗粒泥沙的絮凝机理,为治理钱塘江口提供科学依据。 相似文献
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通过潮汐水流和悬沙淤积物理模型试验,研究厦门高集海堤开口改造工程潮流泥沙问题,研究表明,高集海堤开口后,东、西海域两股水流的汇流区和分流区在高集海堤附近,东海域涨潮流速有所增大,落潮流速有所减小,西海域则相反;随着开口宽度增大,流速变幅增大,开口大于800 m后流速变幅趋缓;海堤开口后净输水方向为自东海域向西海域,有利于厦门湾内水体与外海的交换;高集海堤开口对东渡港区泥沙淤积影响不大.综合分析认为高集海堤开口宽度800～1 000 m较为合适,开口800 m时大潮条件下1d的净输水量约0.91×108m3,东渡北港区港池年平均回淤强度增大0.18 m/a左右,航道淤强增大0.05 m/a左右. 相似文献
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根据海岸河口地区潮流、波浪、泥沙的运动特点及其相互作用机制,考虑了波浪场产生的"波浪辐射应力"和"波流挟沙力"动力要素对潮流场和泥沙运动的影响,在泥沙扩散方程中考虑了紊动水流作用,采用有限元加权集中质量法,建立了考虑波浪作用的潮流泥沙数学模型,并利用锦州港港区的潮流及泥沙资料对模型进行了验证。验证结果表明,潮位吻合良好,流速、流向、含沙量分布基本相似。在此基础上,模拟了工程建设前后,港区附近潮流场和泥沙淤积的变化,分析了泥沙骤淤现象。模拟结果表明,该数学模型能够适用于海岸河口地区潮流、泥沙的模拟,为波浪作用下潮流场和泥沙淤积的预测提供一种新的模拟方法,具有良好的应用前景。 相似文献
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复式河道滩地植物对水流紊动结构影响的试验研究 总被引：9，自引：0，他引：9
利用室内变坡水槽,精细模拟了复式河道滩地不同植物对漫滩水流的干扰作用,并借助声学多普勒测速仪(ADV)观测了不同垂线、不同测点的瞬时流速,计算了水质点三维相对紊动强度,分析了其变化特征,探讨了滩地不同种类植物对水流内部结构的影响。试验发现,滩地植物改变了复式河道水流内部结构,导致植物带内近床面处各个方向水流相对紊动强度明显减弱,横向因植物丛内阻力和流速变化引起的滩区壅水导致横比降增加,主槽相对紊动强度显著增强;植物淹没条件下水流相对紊动强度沿水深的分布明显存在转折点,此位置可以认为是滩地植物对水流影响的“第二边界”。 相似文献
6.
潮汐河段挖入式港池异重流淤积探讨 总被引：1，自引：0，他引：1
盐水与泥沙异重流的基本运动特性是相类似的。文本利用盐水楔扩散问题试验研究的成果,应用到泥沙异重流受潮汐影响的扩散和淤积分析。利用紊动能量损失与扩散系数之间关系,进行潮汐河段异重流问题的研究;并求得紊动能量损失指标G/J<50,属异重流范围。又利用挖入式港地实际淤积资料与淤积计算对比分析,初步认识到异重流淤积量占总量相当大的比例,是由于落潮时无径流量而只有些潮蓄量下泄,流速很小而形成异重流。此外,小潮大径流量时,也有异重流。 在潮汐河段上,由于水位与流速随涨落潮的过程不断地改变,除涨落地期间流速较小外,一般流速较大,即使产生了盐水楔,它也不能持久。因此有人认为有潮汐的盲肠河段或挖入式港池内,不会有异重流的淤积问题。但另有一些人认为水流情况与有潮河段并不完全相同。如在落潮时只有盲肠或港池的潮蓄量外泄,流速很小,有利于形成异重流而淤积。因有上述二种不同看法,故对潮汐河段挖入式港池异重流淤积进行初步探讨。 相似文献
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养马岛连陆海堤对沉积动力环境的影响 总被引：1，自引：0，他引：1
运用水动力和泥沙输运数学模型模拟了养马岛连陆海堤拆除前后的水动力变化以及海底冲淤演变状况。通过对连陆海堤拆除前和后的流场比较,可知连陆海堤拆除后养马岛南部海域流速加大,可达20 cm/a,水流畅通,水体交换能力获得明显的改善;海底蚀淤模拟结果表明,养马岛南部海域淤积情况明显减弱,最大淤积速率仅为1 cm/a,东南侧海域发生侵蚀,最大侵蚀速率为5 cm/a,东侧海域发生普遍淤积,淤积速率在1~5 cm/a之间。连陆海堤拆除后养马岛南部海域海洋环境会得到明显改善。 相似文献
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使用波潮仪、流速计以及浊度计现场测量记录海堤前的波高、潮高、流速和浊度值,与室内测定的浊度和水中悬浮颗粒物含量对应值比较,分析计算浊度与现场测量波高、潮高、流速水动力因素间的相关性,得出堤前泥沙起动的决定性水动力因素。在悬移质运移为主情况下,由于海堤的阻挡,波浪破碎产生的旋涡和紊动是泥沙起动的主要动力因素,泥沙起动量与波高值呈现较高相关性;海堤前复杂水动力条件中,波浪破碎前的流速值与悬移质泥沙起动量相关系数较小,启动流速的主要组成部分是破波产生的旋涡和紊动的流速。 相似文献
10.
长江口北槽黏性细颗粒泥沙特性的试验研究 总被引：2，自引：0，他引：2
选用长江口北槽黏性细颗粒泥沙,在不同盐度的人工海水中通过静水沉降、动水沉降等各种试验手段了解其基本特性。在静水沉降管中观测了胶粒的电化学絮凝过程和重力碰并过程,于不同盐度条件下找出最佳絮凝盐度;并通过黏性细颗粒泥沙在流动海水中絮凝的试验研究,揭示其在动水中絮凝的机理和规律,及不同条件下的起动流速、不淤流速、沉降速度等特征值,从而分析其落淤情况。研究结果表明,长江口北槽细颗粒黏性泥沙的最佳絮凝盐度约为15,起动流速为15~20 cm/s,这与泥沙的淤积固结时间有关,而不淤流速约为60 cm/s。并由试验得到了挟沙力与流速之间的经验关系,以及用于估算不同流速条件下泥沙沉降速度及淤积量的经验公式。这些结果可用于长江口航道的疏浚、整治工作中,具有一定的理论指导意义。 相似文献
11.
The formation of sub-seafloor gas hydrates in marine environments can be described as a coupled transport and thermodynamic process inside a host sediment matrix undergoing structural evolution. The transport processes are driven by the sedimentary load and induced overpressure gradients, controlled by sediment permeability. In order to accurately model the resulting fluid flow profile, the decrease of sediment permeability during hydrate precipitation has to be taken into account, which affects both the transport of solutes and sediment compaction. In this paper, we investigate how total hydrate abundance is affected by regions of low permeability which deflect the flow field in their vicinity. For this purpose, a two-dimensional numerical hydrate system model was set up which permits to quantify this effect in scenarios where changes in water depth cause lateral variations of the thickness of the hydrate stability field, as well as of hydrate saturation and sediment permeability. The microscopic structure of gas hydrate crystals in the host sediment matrix defines the evolution of the permeability reduction during hydrate formation. Grain-coating precipitates have a stronger tendency to clog flow paths through pore throats than do pore-filling precipitates. Our results clearly show that these pore-scale processes affect the large-scale flow field and hydrate abundance. The sensitivity depends on the model geometry and, for a 5° slope of the seafloor, 4.1% relative difference is predicted for the hydrate saturation according to different porosity-permeability relationships. 相似文献
12.
普兰店湾四周大量的滩涂逐步被开发成海参及贝类围堰养殖池塘,致使普兰店湾出现自然岸线不断萎缩、水体交换通道堵塞等系列问题,通过拓宽海湾水体交换通道恢复其水文和水动力条件是重要的手段之一。文章采用 MIKE21 模型对普兰店湾的潮流分布特征进行数值模拟,在潮位、流速模拟验证的基础上,对比分析了养殖围堰拆除工程实施前后普兰店湾的水动力情况。结果表明：养殖围堰拆除区域的局部滩涂流速增大,其值在0.3~0.4 m/s左右变化,围堰拆除对于距离在1.5 km以内的海域有一定影响,而对较远的金州湾及外海的整体流场基本无影响;拆除养殖围堰拓宽了普兰店湾的水域面积,提高了湾内的涨落潮流速,湾内的纳潮量增大了8.535%,位于北岸的养殖池拆除区域流场呈现明显的潮滩特征,上述变化有利于加快潮滩上盐沼植物、海洋生物生境的营养物质交换。 相似文献
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Plant-flow interactions on the surface of tidal wetlands result in flow characteristics that are profoundly different from non-vegetated flows. Reductions in mean flow velocity and turbulence, especially the vertical components, limit vertical mixing and may impact a wide range of processes including geochemical exchanges at the sediment water interface, larval recruitment and dispersion, and sediment deposition and retention. The goal of this paper is to quantify horizontal and vertical components of velocity, turbulence intensity and total turbulent kinetic energy in Spartina alterniflora canopies in southeastern North Carolina and to relate flow characteristics to particulate transport on the marsh surface. Another aim of this paper is to assess the extent to which the distribution of standing biomass affects mean flow and turbulence by comparing S. alterniflora data to other canopy types and through a series of canopy manipulations which altered canopy height and stem densities.The results of this study indicate that flow velocity, turbulence intensity, and total turbulent kinetic energy (TKE) are significantly reduced within the vegetated canopy and that this reduction is inversely related to the amount of biomass present in the water column. Within the canopy, approximately 50% of the initial mean velocity and TKE is reduced within 5 m of the canopy edge. Within the canopy, mean velocity and TKEhoriz usually exceeded vertical velocity or TKEvert and the vertical components of flow were attenuated more strongly than the horizontal. These results suggest that within the vegetation, turbulence contributes more to lateral advection than to vertical mixing. As a result, total suspended solid concentrations were shown to decrease logarithmically with distance from the canopy edge and to decrease at a faster rate in more densely vegetated regions of the canopy (i.e. lower TKEvert) as compared to areas of sparser vegetation (i.e. higher TKEvert). 相似文献
14.
Yinying Huang Yingying Huang Xinglin Du Yiming Li Jiangtao Tian Qiang Chen Youhui Huang Weiwei Lv Ying Yang Zhiquan Liu Yunlong Zhao 《海洋学报(英文版)》2022,41(11):96-107
An ecological optimization project (semi-closed reclamation project) was implemented to control the invasion of Spartina alterniflora, and optimize the habitat of the Chongming Dongtan wetland, in the Changjiang (Yangtze) River Estuary. After project implementation, a macrobenthic ecological survey was conducted in a natural tidal flat and a semi-closed reclamation restoration area within the Chongming Dongtan wetland from 2019 to 2020. Compared with historical data before reclamation, findings showed that the groups, numbers, and species diversity of the macrobenthos increased significantly, and the ecological optimization project resulted in good ecological benefits. In addition, compared to the natural tidal flat, the number of collected macrobenthic phyla, and the macrobenthic density and biomass were significantly lower in the restoration area. Furthermore, the biodiversity index and functional redundancy of natural tidal flats were generally higher, indicating that the community composition and function of natural tidal flats were relatively more stable. Even though the species composition differed between a number of restoration areas and natural tidal flats, there was no difference in functional diversity, indicating that the effect of restoring ecological functions in restoration areas was optimal. Among them, the biodiversity and functional redundancy of Site S2 were significantly reduced, and the ecosystem function was extremely unstable. Habitat heterogeneity, vegetation community and decreasing salinity were the main factors that affected the ecological functions of macrobenthos. The ecological quality was also evaluated; the Transects N3 and N4 showed good quality. The overall ecological quality of the restoration area was generally high, but that of Site S2 was poor and that of Site S2E was merely good, which was mainly due to modifications of the ecological function of macrobenthos. It is suggested that reeds mowing and freshwater species release should be adopted in restoration areas to improve the community function and the environmental disturbance resistance of the macrobenthos. 相似文献
15.
选取海州湾近岸潮流和含沙量实测资料，分析水体紊动强度与含沙量对近岸絮凝体沉降速度的影响，提出了新的沉降速度确定方法。研究表明：淤海州湾近岸泥沙沉降速率大部分在 0.05 ~ 2.50 mm/s 之间，潮周期内泥沙絮凝体的沉降速度
有明显变化。于含沙量较小时，泥沙絮凝体的沉降速度基本随含沙量的增加而增加；含沙量较大时，含沙量与沉降速度呈现出负相关，无论是大潮还是中潮，当含沙量达到 0.7 kg/m3左右时，絮团沉降速度最大，而随着含沙量的增大，絮团沉降速度开始减小。盂在涨落潮垂线平均流速最大时刻，紊动强度达到峰值，含沙量较低时，随着紊动强度增加，沉降速度也随之增加，大潮期间紊动强度对泥沙沉降速度的影响高于中潮。榆新的泥沙沉降速度计算公式不仅考虑了含沙量，还计入了紊动强度 G，大大提高了沉降速度计算值与实测值的相关性。 相似文献
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The combined tidal and wind driven flow and resulting sediment transport in the ocean over a flat bottom at intermediate water depth has been investigated, using a simple one dimensional two-equation turbulence closure model. This model has been verified against field measurements of a tidal flow in the Celtic Sea. The tidal velocity ellipses and the time series of the horizontal velocity components at given elevations above the bottom are well predicted through the water column although there are some deviations between the predicted and measured velocities near the bottom due to the uncertainty of the bottom roughness. For the combined tidal and wind driven flows the velocity profiles, turbulent kinetic energy profiles and surface particle trajectories are predicted for weak and strong winds. Furthermore, the bottom shear stress and the resulting bedload transport have been predicted; the parts of the particle trajectories in the close vicinity of the bottom where the bedload transport exists are displayed. Finally, the direction and magnitude of the surface drift, the depth-averaged mean velocity and the mean bedload transport are given, and the effect of the bottom roughness on the sea surface drift is investigated. 相似文献
18.
海岸盐沼冠层水流平均流速分布的实验研究 总被引：8，自引：0，他引：8
利用室内水槽测量海岸盐沼植物冠层水流平均流速分布，对a)不同属种,b)同属种不同观测位置和流速；c)同属种不同高度;d)同属种不同密度的海岸盐沼植物冠层湍流结构作了分析，产探讨了冠层植物本身及其水流结构对粘性泥沙运动的可能影响；实验结果揭示了冠层上，下水流的复杂性；1）明显的三层结构，即冠层底部，过渡层，冠层上部水体层；2）由于植物的柔弹性，冠层顶部与上层水体相互作用可能产生界面波，导致一个次级流速最大值，在冠层内出现流速反转梯度；3）冠层顶部以上的水体水流切变流速u,（切应力τb)大于冠层内的ux(切应力τb)，冠层内（底部）水流切变流速（切应力τb)的减小有利于粘性泥沙的沉积；4）植物冠层影响湍流强度和扩散。 相似文献
19.
H''、AMBI和M-AMBI指数在黄河口及邻近海域底栖生境健康评价中的适宜性研究 总被引：3，自引：1，他引：2
From a dataset of macrobenthos obtained from 18 cruises from 2004 to 2013 in the Huanghe(Yellow River)Estuary and its adjacent areas,the composition and characteristics of macrobenthos were analyzed,and the applicability of the Shannon-Wiener Index(H′),AZTI's Marine Biotic Index(AMBI) and multivariate AMBI(MAMBI) for assessing benthic habitat quality was compared.The results showed a total of 203 macrobenthos in the study area.The macrobenthos were dominated by polychaetes,followed by mollusks and crustaceans.The macrobenthic ecological groups were dominated by EGI,EGII and EGIII,which respectively accounted for 31.5%,36.0% and 21.2% of the total.There were significant differences between the evaluation results of the three indices.The ecological quality status(EQS) levels given by the AMBI were greater than those given by the H′ and M-AMBI.The AMBI could not reflect the differences between 11 sites but the H′ and M-AMBI could do.Moreover,the three indices responded well to the variations in salinity(S) and dissolved oxygen(DO) in the waters.The H′ and MAMBI also responded sensitively to the differences in physical parameters,such as water depth and sediment texture.The correlation between M-AMBI and environmental pressure gradient data was the strongest.The MAMBI could effectively distinguish degraded conditions from undegraded but the H′ and AMBI could not.Therefore,the M-AMBI reflected benthic habitat health well in the study areas.However,the objectivity of evaluation results of M-AMBI needs further verification by physical,chemical and biological methods.The thresholds also need further discussion. 相似文献