不同侧板结构对八棱柱型人工鱼礁流场效应的影响

为了解侧板结构对八棱柱型人工鱼礁流场效应的影响，实验基于计算流体力学方法(computational fluid dynamics, CFD)，利用大涡模拟(LES)对4种不同侧板结构的八棱柱型人工鱼礁周围流场变化进行数值模拟，并以上升流体积、背涡流体积和向上输运通量等为流场效应指标进行了分析，同时利用水槽实验对数值模型进行验证。结果显示，水槽实验流速与2种尺寸数值模拟流速的均方根误差最大不超过0.065。0°垂直迎流时，2种来流速度下，A型、C型和D型礁的上升流体积较B型礁最大分别高35.6%、244.1%和80.1%，背涡流体积较B型礁最大分别高193.5%、115.8%和88.8%。C型和D型礁的向上输运通量均大于A型礁，且C型礁最大向上输运通量是D型礁的1.29倍。不同迎流角度下，C型礁和D型礁的上升流体积和背涡流体积在4种角度下差异显著，且迎流面投影面积和上升流体积及背涡流体积之间相关系数较小。研究表明，实验所采用的数值模拟准确可靠；侧板数量增加对于提升八棱柱型人工鱼礁流场效应尤其是上升流效应作用明显；下层侧板固定时，上层为倾斜侧板有利于提升礁体的上升流效应，上层为垂直侧板时...     

人工鱼礁的矩形间隙对黑鲷幼鱼聚集效果的影响

为了解人工鱼礁的矩形间隙大小对鱼类行为产生的影响,实验利用特征礁体的不同组合来模拟人工鱼礁矩形间隙的大小,在来流速度分别为19.1、23.4和27.7 cm/s情况下,探讨不同礁体矩形间隙(水平、垂直)的大小对黑鲷幼鱼行为产生的影响,总结出黑鲷幼鱼的喜好流速范围。实验结果表明:当礁体矩形间隙设计为水平38.8 cm时,相对其他情况来说,黑鲷幼鱼具有最大趋礁率43.1%,对应的喜好流速范围为9.6～23.4 cm/s;当礁体矩形间隙设置为垂直20 cm时,黑鲷有最大趋礁率50.1%,对应的喜好流速范围为6.7～27.9 cm/s。总体来说,礁体矩形间隙设计为水平时的集鱼效果要好于礁体矩形间隙设计为垂直时。     

米字型人工鱼礁流场数值模拟与水槽实验的比较

采用LES(大涡模拟)紊流模式,对定常来流速度下按实际尺寸缩小10倍的米字型人工鱼礁单体附近流场进行三维数值模拟,同时利用相同尺寸的水槽实验验证该数值计算方法的可行性。在数值模拟与水槽实验中分别设置了0.2、0.4、0.6、0.8、1.0以及1.2 m/s 6种来流速度,并比较礁体附近三个方向上流速变化的情况。结果表明,数值模拟中约80%的测点速度与水槽实验结果吻合。而且,具有较大差异的值都发生在礁体上方开口中心位置附近的测点,该位置流场变化强烈且水槽实验测量有一定难度,易产生误差,因此对比结果差异较大是可允许的。综合比较结果,初步认为利用三维数值模拟计算方法模拟人工鱼礁的流场变化是可行的,今后可利用该数值计算方法替代复杂的水槽实验,甚至可以对实际投放礁体的原始规格以及所放置的海域进行等比例模拟,更清晰准确地对人工鱼礁周围流场变化进行详细研究。同时对不同结构的人工鱼礁和人工鱼礁群周围的流场进行系统分析,从而实现人工鱼礁的优化配置。     

规模化透水性人工鱼礁阻流效应的数值模拟

为在大尺度海洋模型中合理体现透水性人工鱼礁组合，基于海洋数值模式FVCOM（finite volume community ocean model）模拟了大陈岛拟建人工鱼礁区的水动力情况，比较了阻滞力法、实心礁法和附加底摩擦法在投礁前后的垂向流速、礁顶平面流速、水体向上输运通量和背涡流体积的差异，并根据投礁前后的流速差异，应用经验公式预测了投礁一年后底床泥沙冲淤情况。数值模拟结果表明，礁体组合迎流面产生上升流，礁体背流面流速减小，涨急时刻所形成缓流区长度在礁体组合长度20倍以上，年底床淤积厚度约0.05 m。阻滞力法以减少来流的动态功率密度来模拟礁体对水流的阻滞作用，可有效合理地实现对透水性人工鱼礁流场效应的模拟，避免了实心礁法在透水性鱼礁模拟中过高估计流场效应的问题，也没有附加底摩擦法只适用于低矮礁体的缺陷。阻滞力法可根据透水性礁体的造型、迎流面积、组合个数、布放方式和所处水层而设置各向和各水层的阻流参数，不仅适用于置底型透水性鱼礁，也适用于浮鱼礁。阻滞力法的建立、完善和应用对于今后的人工鱼礁水动力学和生态动力学研究具有重要意义。     

混凝土人工鱼礁选型的初步分析

人工鱼礁的选型优化包括对礁体材料和礁体构造的选择。参考目前现有人工鱼礁结构类型,选取混凝土为设计礁体材料,计算各礁体实体体积、空方体积、表面积及其重量,通过计算找出礁体各性能参数之间的关系。引入礁体每体积混凝土产生的空方体积(ε)和表面积(η)两个优化参数,来衡量礁体的性能。结果表明:框架形礁ε值相对较高,而异体形或组合鱼礁η值相对较高,说明框架形礁体单位体积混凝土产生流态效应最好,异体形或组合结构礁体单位混凝土附着面积较多。同时引入有效空方体积概念,进一步说明礁体结构与流态的关系。     

塔型桁架人工鱼礁流场效应及稳定性

本研究利用物理模型试验和粒子图像测速技术,对塔型桁架人工鱼礁模型在6种换算流速0.031 m/s、0.063 m/s、0.095 m/s、0.126 m/s、0.158 m/s和0.190 m/s (实际流速0.2 m/s, 0.4 m/s, 0.6 m/s, 0.8 m/s, 1.0 m/s和1.2 m/s)下产生的流场效应与物理稳定性进行研究。结果表明,流速达到1.2m/s时,礁体不会发生漂移和倾覆,说明该礁型具有良好的稳定性。单体礁在45°和90°迎流方式下,最大上升流流速和上升流平均流速随来流速度增加而递增,90°摆放单体礁最大上升流流速为来流速度的15.6%～21.0%, 45°摆放单体礁最大上升流流速为来流速度的16.3%～23.5%;上升流面积和高度随来流速度的增大先增加后减小,均在来流速度为0.095 m/s时出现最大值;缓流区面积均随来流速度的增加而减小;在相同来流速度下, 45°迎流时礁体缓流区面积大于90°迎流;在45°和90°摆放方式下,缓流区长度与礁高比值均随来流速度的增加呈下降趋势,且下降趋势逐渐平缓;45°迎流时缓流区长度为礁体高度的13～24倍, 90°迎流时缓流区长度为礁体高度的11～22倍。塔型桁架人工鱼礁礁体前后没有涡流形成,但具有较好的缓流作用,在礁体后方形成了较大规模的缓流区。     

复合M型人工鱼礁粒子图像测速二维流场试验研究

为了获得复合M型人工鱼礁的流场效应,为鱼礁的结构设计提供理论依据,选取3个不同水流流速(6.7 cm/s、11.0 cm/s、18.0 cm/s),采用粒子图像测速(PIV)技术,对复合M型人工鱼礁的二维流场进行测试。结果表明:礁体迎流面和背流面分别产生上升流和背涡流,其规模随着来流速度的增加而增大;当鱼礁圆柱孔与流向夹角为90°时所产生的上升流高度为礁高的53%~90%,背涡流面积为迎流面积的0.7~1.3倍;夹角为0°时上升流高度为礁高的33%~83%,背涡流面积为迎流面积的40%~60%;90°工况下上升流平均流速是0°工况时的1.1~2.7倍,背涡流的最大回流速度为0°时的3.0~9.0倍。鱼礁投放时采用鱼礁圆柱孔与水流流向垂直的摆放形式流态较好。     

现场海域人工鱼礁分布状态聚类分析

人工鱼礁的流场营造、鱼类诱集等建设目标,一般是通过单位鱼礁、鱼礁群等不同规模的形式实现的;实际投放的成千上百个人工鱼礁处于何种分布状态、它们是否满足单位鱼礁等规模要求,是非常值得关注的课题。本文利用空间聚类分析,借助基于划分的算法、基于层次的算法和基于约束的算法对投放后的鱼礁进行划分、归类或剔除,并选择单位鱼礁的重心、影响面积、鱼礁单体数量以及礁体间距4个指标进行比较分析,探讨人工鱼礁实际的组合聚类模式。结果显示3种空间聚类算法误差的排列顺序为：约束算法<划分算法<层次算法。通过对比分析,在基于约束的聚类算法下,最能反映人工鱼礁的实际集聚情况。     

潮流作用下人工鱼礁山海域泥沙输运的数值模拟研究

为探究人工鱼礁投放后对海域底质的影响,实验基于海洋数值模型FVCOM (finite volume community ocean model)及其泥沙计算模块,对嵊泗马鞍列岛的人工鱼礁山的流场效应、悬沙和底床泥沙冲淤效果进行了数值模拟研究。数值模型中圆台型堆积人工鱼礁山设置为直径100 m、高度10 m,将人工鱼礁山部分简化为密闭空间并减去相应高度的水深,以体现潮流作用下鱼礁山周围的泥沙悬浮、底床冲淤效应。通过对大小潮期间涨急、落急时刻流场的分析,结果发现鱼礁山对流速的影响主要体现在鱼礁山附近,礁体上方及潮流主轴两侧的底层流速增加,背流面一侧流速大幅减弱。鱼礁山投放前后悬浮泥沙含量的差异与流场变化趋势比较接近,最大值不超过0.01 g/L。海床的泥沙冲淤结果在人工鱼礁山周围表现为沿涨、落潮主轴方向淤积,两侧冲刷,冲淤结果在±0.5 m左右,且水平影响范围在鱼礁山2倍直径,即约200 m以内,由人工鱼礁引起的泥沙输运过程是一个局部变化过程。研究表明,为避免局部过度冲刷,需对鱼礁山潮流椭圆短轴侧的附近海底使用特殊护底型礁体进行加固处理。潮流速度过大、且底质易严重冲淤的海域不适合建设人工鱼礁山。     

以数值实验为基础的米字型鱼礁布设模式差异下的流场效率

人工鱼礁投放规模是鱼礁建设的核心问题之一,其中礁体数量与布设间距不仅表征了鱼礁规模的范围和密度,而且也决定着人工鱼礁流场效率。本研究采用数值实验方法,对典型结构边长为l的米字型人工鱼礁在4种投放量(2×2、3×3、4×4和5×5)、7种布设间距(0 l、0.5 l、1.0 l、1.5 l、2.0 l、3.0 l和4.0 l)下的流场相对体积、相对高度、相对长度等流场效率特性进行比较分析。结果显示,当上升流目标流速比分别为小于0.10、0.10～0.15和大于0.15倍时,上升流流场存在协同效应的最大布设间距分别为4.0 l、3.0 l、2.0 l,背涡流目标速度比下最大间距均为3.0 l;人工鱼礁投放量越多,上升流与背涡流相对体积越大,平均相对体积增长率越低,0.5 l布设间距的上升流相对体积与鱼礁单体相对流场体积最大,1.5 l布设间距的背涡流相对体积与鱼礁单体相对流场体积最大;上升流相对高度随投放量增加以1.01倍速率增加,随布设间距增加以0.90倍速率降低,背涡流相对长度随布设间距的增加先增后降,相对长度最大值位于1.0 l处。     

A simulation application to improve the operational efficiency of the wholesale fish market in Taiwan

Abstract

This paper presents the applications of two simulation models developed for the Pu‐Shin wholesale fish market: the current operational model and the alternative operational model. This study analyses the possible influence on the wholesale fish system by manipulating the number of porters in the alternative operational model. Cost‐benefit analysis is conducted to compare the two models. The results suggest ways to improve the operational efficiency of the wholesale fish market in Taiwan.     

水流作用下筏式养殖设施动力响应的数值模拟

利用有限单元法建立了水流作用下筏式养殖设施动力响应的数学计算模型,通过数值求解对浮标和吊笼结构的最大位移以及锚绳受力进行分析。计算机模拟结果表明,筏绳在水流作用下产生明显的变形,其形态变化与实际基本相符。当流向一定时,浮标和吊笼的最大位移值以及左右两侧的锚绳受力均随流速的增加而增大。其中,浮标最大位移值7.6m,吊笼最大位移值9.6m。当流速一定时,浮标和吊笼的最大位移值与右侧锚绳受力随着来流角度的增加而增大。左侧锚绳力受来流方向变化影响不明显,其最大值为3 780N。     

A spatial model of population dynamics of the early life stages of Japanese sardine, Sardinops melanostictus, off the Pacific coast of Japan

We constructed a numerical model reproducing the transport, survival and individual growth of the early life stages of Japanese sardine, Sardinops melanostictus, off the Pacific coast of Japan during 1978–93. The causes of early life stage mortality, including the influence of the effects of the spatial relationship between the spawning grounds and the Kuroshio on the mortality rate, were investigated. Survival and transport from egg stage to 60 days after spawning were modelled daily in a 1 × 1 degree mesh cell and individual growth in the period was modelled in each region (Kuroshio, Inshore, Offshore and Transition regions). Individual growth and survival from 60 to 180 days after spawning were modelled daily in the Transition region. Environmental data were taken from outside the model system. Our simulation indicates that survival variability in the larval stage (5–25 mm in standard length) is the key factor in determining the year‐class strength. The simulation revealed that strong year classes occurred with good survival in the spawning ground and whilst entrained in the Kuroshio current being transported to the main feeding grounds in the Transition region. The simulation also indicated that survival rates in 1988–93 were low in the Inshore, Kuroshio and Offshore regions, which depressed the year‐class strength during that period.     

Evaluation of stock management procedures for walleye pollock in northern waters of the Sea of Japan using a simulation

To evaluate walleye pollock stock management procedures in the northern waters of the Sea of Japan, 30-year population dynamics, including uncertainties, were forecast. Errors in current stock size estimation, variability in future recruitment and changes in future fishing mortalities were incorporated. Results of virtual population analysis (VPA) from resampled catch-at-age data with bootstrap methods was used as the current stock size estimation with uncertainty. Performances of each scenario were evaluated using conservation, utilization, stability and reliability factors. Twenty-two management scenarios and continuing the current fishing mortality were evaluated. Scenarios with minor regulation changes and continuing the current fishing mortality showed poor stock conservation performances. Scenarios with minor regulation changes produced good short-term but poor long-term utilization. Stabilities were poor in continuing the current fishing mortality and fishing ban scenarios. Reliability in all scenarios after 30 years was smaller than in continuing the current fishing mortality; however, small differences among scenarios were observed. The simulation results indicated that multilateral assessment is needed to evaluate the management candidates. Uncertainty caused by recruitment variability mostly affected future population dynamics. The role of simulations in the production of effective scientific advice is discussed.     

水流作用下重力式网箱网衣张力分布

在水流作用下,网箱网衣要承受很大的水流作用力,在网箱实际使用中破网逃鱼现象时常发生。网衣属于柔性结构物,在外部荷载作用下会发生较大的变形和位移,因此其受力和变形特性较为特殊。为了获得水流作用下重力式网箱网衣的张力分布,从而为设计和生产提供理论参考依据,利用集中质量的方法建立了水流作用下网箱网衣受力和变形的数学计算模型。利用此数学模型对重力式网箱网衣在不同配重模式和网目形状下的变形和张力分布进行了数值模拟。通过数值模拟研究发现,网箱网衣张力分布形式和网目形状关系密切,配重形式对其影响较小。相同工况条件下,配置底图时网衣所受最大张力略大于单独沉子配重形式,同时菱形网目网衣所受最大张力略大于正方形网目的受力。     

圆柱形网箱锚绳受力特性的数值模拟

根据动力学原理,研究在水流作用下圆柱形网箱锚绳的受力特性,导出锚绳形状和张力的一阶微分方程组,并利用四阶Runge-Kutta计算法,结合Matlab工具,对圆柱形网箱的系泊锚绳,在水流速度、水流冲角、水深和锚绳长度等参数下的空间位置及张力变化进行数值求解和仿真模拟。模拟结果显示,在给定的初始条件下,锚绳长度对锚绳的空间位置影响最显著,水流冲角对锚绳张力的影响最大,水深对形状和张力的影响最不明显;锚绳张力随长度的增加而减小,随水流冲角、流速的增加而增加。     

Numerical simulations of the seasonal circulation patterns and thermohaline structures of Prince William Sound,Alaska

A three‐dimensional, primitive‐equation ocean circulation model was applied to Prince William Sound, Alaska (3D‐PWS circulation model), under forcing of an ocean tide, freshwater runoff, surface heat flux, Alaska Coastal Current (ACC) throughflow (inflow/outflow), and daily (synoptic), spatially varying winds. The 3D structures and seasonal cycles of the circulation patterns, temperature, salinity (density), and mixed layer are examined. Freshwater runoff significantly contributes to the basin‐scale cyclonic circulation, which was not addressed in the previous simulations. Two typical circulation regimes, cyclonic and anticyclonic, characterize the complex flow patterns that depend on the intensities of the ACC thoughflow, freshwater discharge, and the synoptic wind. The spring (April–May) circulation pattern is characterized by a weak (maximum current 0.1 ms^?1) anticyclonic flow in the central Sound, while the autumn (September–October) circulation is dominated by a basin‐scale, cyclonic gyre (maximum current 0.2 ms^?1) due to the increase of the ACC throughflow and the maximum freshwater influence. During the summer, the circulation includes the cyclonic and anticyclonic gyres. During the winter, the circulation pattern is controlled by the basin‐scale cyclonic gyre and surface drift driven by the strong north‐easterly (south‐westward) wind forcing. The seasonal cycles of temperature (T) and salinity (S) vs. depth compare well with the observations. The simulated spring and autumn surface circulation patterns compare qualitatively well with the towed ADCP (acoustic Doppler current profilers) flow patterns and dynamic height patterns in the central Sound. An application of this model to zooplankton overwintering is discussed.     

Simulation of inorganic nitrogen dynamics and shrimp survival in an intensive shrimp culture system

Nitrogenous wastes are major concerns in shrimp production and as a component of total farm wastes that impact the aquatic environment. This study describes a simulation model of the role of heterotrophic and nitrifying bacteria on nitrogen dynamics in intensive Litopenaeus vannamei (Boone) culture systems using different feeds and feeding strategies. The model represents: (i) use and remineralization by heterotrophic bacteria of nitrogen wastes and ammonia excreted by shrimp; and (ii) nitrification. The model was quantified using published and unpublished information. The model is multivariate, deterministic and uses a compartment model structure based on difference equations. Evaluation of the model consisted of simulating two indoor and one outdoor experiment that examined the effects of different feeds and feeding levels on nitrogen dynamics. In summary, the model is capable of qualitatively following inorganic nitrogen dynamics. Simulations investigating the effect of heterotrophic remineralization on total inorganic nitrogen suggested that this process may contribute up to 97% of the inorganic nitrogen in the system. This indicates that strategies to increase production, such as increases in feed protein levels or feeding rates, should be carefully evaluated before they are implemented. Future studies need to address bacterial community role in these systems and inorganic nitrogen toxicity mechanisms.     

华南沿海贝类体镉的调查与膳食暴露评估

根据2009年对广东、广西沿海主要贝类养殖区太平洋牡蛎（Crassostrea gigas）、翡翠贻贝（Perna viridis）、文蛤（Meretrix meretrix）和菲律宾蛤仔（Ruditapes philiparum）等贝类体镉（Cd）的调查结果,采用随机模拟的概率评估方法,对贝类体Cd的膳食暴露量进行了评估,对评估的不确定性和变异性进行了定量分析和讨论。结果表明,调查海域贝类w（Cd）存在显著性差异,所有样品中w（Cd）均低于无公害水产品中有毒有害物质限量标准值。将评估结果与WHO/FAO的食品添加剂联合专家委员会推荐的Cd的暂定每周耐受摄入量（PTWI）相比,贝类体Cd的膳食暴露量低于PTWI值,但在P95的高百分位水平下,贝类Cd的膳食暴露量占PTWI的比例较高（29.1%-57.4%）。建议采取相应措施,降低贝类体Cd的膳食暴露量。     

基于系统动力学模型的渔业资源增殖放流效应分析

文章从系统动力学角度出发,着眼于动态系统的整体统筹,综合考虑渔业、生态和社会三方面要素,对山东省中国对虾（Penaeus chinensis）增殖放流渔业进行了系统动力学建模仿真,并通过对预测结果的比较分析,探讨了合理的放流量、捕捞努力量等决策变量,以期为渔业决策者提供有益的参考。文中提出的方法亦可用于对渔业资源生物量、产量、社会效益、生态效应的评估和预报。