共查询到20条相似文献，搜索用时 78 毫秒
1.
布设间距对人工鱼礁流场效应影响的数值模拟 总被引：10，自引：0，他引：10
人工鱼礁在海中不同的布局方式会产生不同的流场效应.通过水槽与风洞模型实验很难对组合鱼礁流场全局进行观测,为此提出1种基于CFD原理的人工鱼礁流场特性的计算机数值模拟方法,模拟了不同流速条件下布设间距对方形组合礁体流场效应的影响.结果表明:数值模拟较好地反映了人工鱼礁周围上升流和背涡流的分布情况;当两礁体布设间距为1.5倍礁体尺寸时,所产生的上升流高度达到最大值;当布设间距为1倍/时,其上升流的影响面积为最大;当布设间距为1.5倍时所产生的背涡流效果最好;两礁体之间的最佳布设间距应为礁体尺寸的1～1.5倍.数值模拟结果与风洞实验结果基本相符,该结论可为人工鱼礁实际投放提供理论参考. 相似文献
2.
三种叠放形式的圆管型人工鱼礁流场效应数值模拟与PIV试验研究 总被引：6，自引：0，他引：6
人工鱼礁单体按不同的数量和排列方式组合投放会产生不同的流场效应。圆管型礁为目前黄渤海区增殖礁的重要礁体型式,为优化该礁体的投放数量与排列方式,选择了3种不同叠放个数(1个、3个和6个)的圆管礁,设定了5个流速梯度(4.5、9.0、13.5、18.0和22.5cm/s),利用PIV粒子图像测速技术和Fluent数值模拟软件对圆管型人工鱼礁的流场进行水槽模型试验和数值模拟。结果表明,数值模拟结果与水槽试验结果基本吻合,误差在20%以下,表明数值模拟能够反映人工鱼礁的流场效应;当礁体叠放个数一定时,最大上升流流速、上升流高度和上升流面积均随来流速度的增加而增大,背涡流面积呈现不规则的变化;当来流速度一定时,最大上升流流速、上升流面积、上升流高度和背涡流面积均随礁体叠放个数的增加而增大。 相似文献
3.
合理的人工鱼礁组合可以有效改善投放水域的流场效应,提高投放水域底层与上层水体之间的扰动。通过使用并行大涡模拟模式及被动示踪物模块,并通过调整人工鱼礁布设间距,研究了在不同背景流速条件(0.1、0.5、0.6和1.0 m/s)下,在不同的横向间距(1L、2L、3L)(L表示人工鱼礁的边长)或纵向间距(1L、2L、3L、4L、5L)情况下,方型人工鱼礁对上升流体积、营养盐的抬升和垂向涡黏系数的影响。研究结果表明,在同一布置条件下,单排布置下的三块人工鱼礁形成的上升流体积大小与来流速度成正相关,体积随来流流速增加而增大6.4%～80.5%;在同一流速条件下,上升流体积大小与纵向布置的间距成正比,与横向布置的间距成反比;在横向布置条件下,当来流速度为1.0 m/s、布设间距为1L时,上升流体积参数最佳。总体来说,上升流体积参数、示踪物浓度差和垂向涡黏性系数均显示横向布置优于纵向布置,相较于布设间距,来流速度是影响上升流体积最重要的因素。 相似文献
4.
《中国海洋大学学报(自然科学版)》2016,(9)
本文采用RNG K-ε湍流模型和SIMPLEC数值模拟方法,分析了不同雷诺数条件下,布设间距和摆放方式对三圆管型人工鱼礁流场效应的影响。研究显示:采用FLUENT软件模拟,雷诺数能较好地反应人工鱼礁上升流和背涡流的分布情况,上升流的规模和强度随雷诺数的增大而增加,背涡流随雷诺数变化的趋势不明显。三圆管型人工鱼礁横向组合方式下,2个单位礁布设间距等于礁体尺寸时,获得的上升流和背涡流的规模和强度最大;纵向组合方式下,2个单位礁布设间距为礁体尺寸的1.5~2.0倍时,获得的上升流和背涡流的规模和强度最大。在不同实验流速和波况下三圆管型人工鱼礁的抗滑移系数、抗翻滚系数均大于1。研究结果表明,数值模拟能够较好地反应布设间距对礁体周围流场效应的影响,可为人工鱼礁的实际投放提供理论参考。 相似文献
5.
根据2012年—2013年对霞浦人工鱼礁海域调查所获得的实验数据,应用CFD软件,对礁区投放的三类不同结构单位的鱼礁组合在非定常流作用下的三维流场进行了数值模拟试验,分析了各鱼礁组合之间的流场差异,并估算了诸营养盐垂直输送通量。研究表明:三种鱼礁迎流面上升流最大高度为礁高的2.27~3.73倍,上升流最大速度与来流速度之比为0.40~0.72,上升流平均速度与来流速度之比为0.10~0.17;计算域内单位鱼礁组合上升流平均速度为10–2 cm/s量级,三种单位鱼礁组合区域营养盐垂直通量大小关系为:方型鱼礁船礁梯形台鱼礁,方型鱼礁区4PO??-P、3NO?-N、3Si O??-Si的平均垂直通量分别为438.3 mg/(m2·d)、2212.5 mg/(m2·d)、7288.3 mg/(m2·d),鱼礁投放会改善该海域的水动力环境,形成典型的上升流区,海域初级生产力得以明显提升。 相似文献
6.
为研究空心梯形台人工鱼礁体布设间距的变化对其水动力特性的影响,通过物模实验实测了开口比为0.1的梯形台人工鱼礁体在平行水流方向布设间距为1.0L、2.0L、3.0L(L为礁体的底边边长),前后共6个测点的流速及礁体受力。分析得到了双礁体的上升流规模、阻力系数在平行和垂直水流方向随布设间距变化的规律。采用计算流体动力学(Computational Fluid Dynamics, CFD)方法模拟了双礁体分别在垂直水流方向布设间距为0.5L、1.0L、1.5L、2.0L,平行水流方向布设间距为0.5L、1.0L、2.0L、3.0L、4.0L时的水动力场。结果表明:本研究数模与物模相同工况下,即双礁体在平行水流方向布设间距1.0L、2.0L、3.0L时,数值模拟的流速值和阻力值与相应的实验结果吻合较好,说明数值模拟方法可行,结果可靠。数值模拟结果得到双礁体的上升流规模、阻力系数均与垂直水流方向布设间距成反比。当垂直水流方向布设间距为0.5L时,流场效应最佳;双礁体的上升流规模随平行水流方向布设间距成正比,前方礁体阻力系数变化幅度较小,后方礁体阻力系数逐渐增大;当平行水流方向布设间距为4.0L时,流场效应最佳。本文研究结果可为单位鱼礁布局设计和参数确定提供参考。 相似文献
7.
8.
方型人工鱼礁水动力性能试验研究 总被引：4，自引：0，他引：4
人工鱼礁水动力性能的研究对于鱼礁的设计、礁区布局具有非常重要的意义。本研究设计2种方型人工鱼礁模型,在回流水槽中测量不同水流速度下的鱼礁阻力,并计算阻力系数(Cd)与雷诺数(Re)。结果表明:无盖礁体模型正面迎流时(θ=0(°)),当Re超过7.5×104时,Cd为1.64,其自动模型区域为Re>7.5×104;45(°)方向(θ=45(°))迎流时,当Re超过6.36×104时,Cd为1.3,其自动模型区域为Re>6.36×104。有盖礁体模型正面迎流时,当Re超过6×104时,Cd为1.69,其自动模型区域为Re>6×104;45(°)方向迎流时,当Re超过8.48×104时,Cd为1.43,其自动模型区域为Re>8.5×104。1种礁体模型在不同迎流方式下所受的阻力不同,45(°)方向迎流比正面迎流时的阻力大。在相同的迎流方式下,有盖礁体所受的阻力比无盖礁体大。 相似文献
9.
基于Fluent流体计算平台,运用大涡模拟方法对亚临界雷诺数Re=3900下“X”形排列五圆柱体结构群三维绕流特性进行研究,主要分析来流攻角α与间距比L/D两个关键参数对五圆柱体结构群的尾流区三维涡结构演化与流体力系数的影响,并揭示其内在流动互扰机理。研究表明:来流攻角和间距比的变化对五圆柱体结构群流动控制及互扰效应的影响显著。在小间距比工况下,观察到柱体群间隙区域内流体高速流动的现象,导致五圆柱体之间的互扰作用十分强烈。间隙流对中间圆柱体和下游圆柱体有较强的冲击作用,对其表面的流体力分布特性有显著的影响。另外,大间距比工况下,当α=0°与L/D≥5.0工况时,柱体群尾流效应强于其间隙流效应。当α=22.5°与L/D=7.0时,位于下游与中间处的圆柱体流体绕流特性存在较大差异。而当α=45°与L/D≥6.0时,位于上游与中间处的圆柱体尾流区均会产生正负交替的漩涡结构。 相似文献
10.
海流对于海洋渔业、海洋表层初级生产力分布、海洋物质输运等理化生现象有着重要影响。文章利用海洋再分析流场资料,简要分析印度洋海区和南海海区(20°S—30°N,30°E—130°E)的流场年平均以及季节变化特点,得出以下结论:1南海海区流场的季节变化显著,受到季风、黑潮和地形的共同影响作用,在东北季风期间存在沿粤东沿岸至海南岛南侧转向沿越南沿岸的一支流系,该流系的强度变化影响爪哇海等南海南侧海区流场变化。2苏拉威西岛东侧和加里曼丹岛西侧流系有明显的季节变化,在流动强盛的时期这两支流系均是偏南向流动;从爪哇海流出的海流常年存在,夏季附近流速最大,最大流速分布在1.0m/s。3赤道印度洋海区和非洲东岸的沿岸流存在明显的季节变化,上层海区流动的低流速区存在流向切变;沿岸流最大流速在5-9月出现,可达1.8m/s以上,而赤道流系则在11月,可达0.8m/s以上。 相似文献
11.
Arne Schnack-Friedrichsen Angela M. Davis Jim D. Bennell Dei G. Huws 《Marine Georesources & Geotechnology》2001,19(4):221-243
The interdependence between the seismo-acoustic properties of a marine sediment and its geotechnical/physical parameters has been known for many years, and it has been postulated that this should allow the extraction of geotechnical information from seismic data. Though in the literature many correlations have been published for the surficial layer, there is a lack of information for greater sediment depths. In this article, a desktop study on a synthetic seafloor model illustrates how the application of published near-surface prediction equations to subsurface sediments (up to several tens of meters burial depth) can lead to spurious predictions. To test this further, acoustic and geotechnical properties were measured on a number of sediment core samples, some of which were subjected to loading in acoustically-equipped consolidation cells (oedometers) to simulate greater burial depth conditions. For low effective pressures (representing small burial depths extending to around 10 meters subsurface), the general applicability of established relationships was confirmed: the prediction of porosity, bulk density, and mean grain size from acoustic velocity and impedance appears generally possible for the investigated sedimentary environments. As effective pressure increases through, the observed relationships deviate more and more from the established ones for the near-surface area. For the samples tested in this study, in some instances increasing pressure even resulted in decreasing velocities. There are several possible explanations for this abnormal behavior, including the presence of gas, overconsolidation, or bimodal grain size distribution. The results indicate that an appropriate depth correction must be introduced into the published prediction equations in order to obtain reliable estimates of physical sediment properties for greater subsurface depths. 相似文献
12.
Shigehisa Nakamura 《Marine Geodesy》2000,23(1):55-61
Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone. 相似文献
13.
The effect of different fixation and storage protocols on the flow cytometric (FCM) simultaneous analysis of bacterioplankton and phytoplankton in coastal seawater samples (Mediterranean coastal lagoons) was investigated. FCM measurements (cell number, fluorescence and scatter characteristics) were obtained through DAPI staining. Three fixatives [glutaraldehyde (GA), formaldehyde (FA) and paraformaldehyde (PFA)] and two storage (3 months duration) methods (5 °C and −196 °C) were tested. Two dominant populations were detected in studied samples: bacteria and eukaryotic picophytoplankton. Adding fixatives (2% final concentration) appears necessary to obtain FCM exhaustive counts of all the bacteria and phytoplanktonic cells. This was related to the permeation effect of fixatives which allowed a better DAPI staining of the cells. Maximum fluorescence, i.e. optimal staining of the cells was obtained with FA or PFA, and significant lower fluorescences with GA. Fixed samples stored at 5 °C induced rapid cell loss. Only storage in liquid nitrogen of samples fixed with FA or PFA, allows mid-term (≥4 months) preservation of bacteria or picophytoplankton cell numbers, and limited evolution of DAPI-induced fluorescence and scatter characteristics. 相似文献
14.
15.
《海洋学报(英文版)》2014,(9):F0003-F0003
<正>Acta Oceanologica Sinica(AOS)is a comprehensive academic journal edited by the Editorial Committee of Acta Oceanologica Sinica and is designed to provide a forum for important research papers of the marine scientific community which reflect the information on a worldwide basis.The journal publishes scholarly papers on marine science and technology,including physics,chemistry,biology, 相似文献
16.
The relationship between the flux of exotic benthic foraminiferal tests (i.e. tests which are supplied from open-sea sources alone) in a tidal inlet and that of bulk sediment was analysed, which can be expressed as two first-order linear equations. According to this relationship, in order to determine net sediment transport directions in the entrance, the test concentration in surficial sediments of the tidal basin can be compared against a ‘ critical level ’. The critical level is determined for the conditions that no net transport of bulk sediment is present within the entrance. If the observed concentration (averaged over the tidal basin) is higher than the simulated critical level, then the net sediment transport is directed to landward. This method is applied to the analysis of net sand transport at Christchurch Harbour, a tidal inlet system located in southern England. In this investigation, concentrations of exotic foraminiferal tests in the surficial sediments of the tidal basin and ebb tidal delta area were obtained from the analysis of sea-bed sediment samples. A series of probable critical levels were calculated based upon the data sets with regard to: (1) sediment discharge from the rivers; (2) magnitude of sediment discharge within the entrance during the ebb; (3) the test concentration outside the harbour; (4) the thickness of the moving layer; and (5) two parameters associated with dispersive processes. The results show that the concentration in the tidal basin sediment is higher than a number of simulated critical concentrations for representative cases. Consequently, the high level of the concentration of exotic benthic foraminiferal tests within the harbour should be explained as a result of landward net transport of sands within the entrance. 相似文献
17.
18.
Rahul Sharma 《Marine Georesources & Geotechnology》2000,18(3):237-250
Observations on seafloor features from subbottom profiling and seabed photography data show that the undisturbed and natural conditions before the benthic disturbance undergo a substantial change after operation of the disturber. The effects can be seen in the form of deep trenches and grooves, formed by the action of the sleds and the pumping of the sediment along its path, as well as sediment piles on either side of the track. Biological traces such as fecal coils, casts, tubes, burrows, and trails get obliterated in the areas of disturbance and resedimentation. The smooth, uniform nature of the seafloor observed in predisturbance phase shows microtopographic changes in and around the disturbed area as a result of sediment excavation and resettlement. Vertical mixing as well as lateral transport of sediment alter the geological, biological, physical, and chemical conditions on the seafloor, which need to be monitored over time to assess the process and the time taken for restoration of environmental conditions. 相似文献
19.
Vance P. Vicente 《Marine Ecology》1989,10(2):179-191
Abstract. Long-term changes in the distributional patterns of commercial sponges ( Spongia spp. and Hippospongia spp.) within the West Indian Region indicates that: 1) commercial sponges had a widespread distribution throughout the whole West Indian Region and were ubiquitous in very shallow water until about the first half of the present century; 2) they were fished commercially not only in the traditional northern Caribbean sites (Florida, Gulf of Mexico, Bahamas) but also in the Greater ( e. g. , Hispaniola, Jamaica) and Lesser Antilles; and 3) they became extinct throughout most of the Lesser Antilles ( e. g. , Puerto Rico, Vieques, St. Thomas) sometime during the first half of this century. Mortalities of spongiids within the Antilles were found to differ from other marine mortalities in that: 1) species disappeared from a large region; 2) species vanished from different habitats and depths; and 3) natural populations never recovered. Species richness patterns suggest that commercial sponge genera ( Spongia and Hippospongia ) evolved under slightly cooler elimatic conditions than those found at present, and that these extinctions occurred as a direct or indirect effect of positive thermal anomalies in sea surface and atmospheric temperatures between 1900–1950. The concept that species diversity is stable on a regional scale is questioned. 相似文献
20.
The behaviour of an axially pre-loaded cylindrical member of an offshore structure, hit by a supply ship, has been investigated. The effects of axial pre-loading on the dynamic properties of members, the extent of damage and propagation of dynamic instability in the tubular members have also been investigated. Numerical models have been validated using available experimental data from the literature although these are mostly static with no pre-loading. Axial pre-loading was found to change the dynamic characteristics of some cylindrical members quite dramatically while it had no significant effect on others. The study examined whether there was any change in the behaviour between local and global modes when the loading was dynamic rather than static. The effect of damping on the dynamic instability of axially pre-loaded tubes under lateral dynamic loads was also studied. It was observed that for some geometries the quasi-static response can be used to define the boundary between bounded and unbounded dynamic responses. The main contribution of this study, compared with previous investigations reported in the literature, is that both pre-loading and dynamic effects have been included. 相似文献