转盘式网箱清洗装置设计与模拟试验

在网箱养殖过程中,网衣附着物的产生影响了网箱内部水流交换和鱼类的正常生长。设计了一套转盘式网箱清洗装置,用于解决网衣附着问题。根据选取的水泵(额定流量Q_额=30 L/min、额定压力p_额=20 MPa),应用连续性方程和伯努利方程,通过水力学计算并使用流量测速法进行实物样机试验,确定了清洗盘的最优喷嘴直径d=0.6 mm,其射流速度v=196.41 m/s、射流压力p=19.3 MPa。运用基于有限体积法的计算流体力学软件FLUENT对高压水射流场进行数值模拟分析,确定清洗盘与网衣的最大工作距离为10.3 mm;验证了使用Realizable k-ε湍流模型可以精确地计算此射流工况下的水动力学参数。结果表明,设计的网箱清洗装置可以满足网衣清洗需求,为网箱清洗装置的设计和优化提供参考。     

射流式吸鱼泵关键技术研究及设计

为实现深水网箱规模化养殖渔获的自动起捕,依据射流泵的工作原理,提出了射流式吸鱼泵的结构优化设计方案。基于能量方程,对工作泵的压力计算表达式进行了推导,并对射流式吸鱼泵的性能参数进行了计算。射流泵压力校核结果表明,选配的工作泵可满足设计要求。     

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。     

深水网箱圆台形囊网的设计与制作

深水网箱囊网受水流推动,形状随水阻力大小而变化。囊网形状的变化与养殖容积有关,并直接影响了网箱养殖效果。通过分析认为,圆台形重力式柔性囊网有较好的抗流效果,更适合于深水网箱养殖作业。通过实物试验,报道了圆台形囊网在流速0.45-0.75 m·s-1时的外形设计、配重及制作方法,为强流下的深水网箱囊网制作提供参考。     

高压射流式水下洗网机喷嘴的设计

为解决深水网箱养殖过程中因网衣附着生物而影响水体交换,并给换网及网衣清洗带来极大困难等问题,开发水下洗网机并提高水下洗网机的清洗效率,是深水网箱养殖的重要配套装备与技术。通过对高压射流水下洗网机工作原理的分析,基于能量方程,推导出洗网机关键部件喷嘴的结构几何参数计算表达式。合理选择高压水发生系统的压力和流量,计算出喷嘴的孔径与长径比。在此基础上计算高压射流水下洗网机的水力参数,为进一步优化洗网机结构提供理论依据。     

水流作用下自升降式张力腿网箱水动力学特性试验研究

自升降式张力腿网箱因其在水流作用下能够下潜到水中,具有在恶劣海况条件下,避免海水表面的风浪冲击,降低网箱系统被破坏风险的优点,具有良好的市场前景.根据田内准则,运用水槽模型试验方法,研究了周长60 m,网高16 m张力腿网箱在水流作用下的缆绳张力、网箱下潜深度、容积损失率与流速的关系.结果显示:张力腿网箱缆绳张力随流速...     

网箱的概念简化与力学计算

网箱作为刚性体和柔性体的复合体,工作状态同时处于流场和波浪场的复合作用,直接对网箱进行力学计算目前还存在一定困难.本研究通过对网箱的概念进行简化,通过对网箱概念模型进行力学计算,来定性地探讨网箱的基本性能,以期对网箱的设计提供理论上的参考依据.研究结果表明,水流对网箱的变形有较大影响,而配重对于改善网箱变形的作用是有限度的;作者开发的网箱耐流技术可以很好地改善网箱变形,减少网箱容积损失,当配置为2.0 N流速为1 m/s时,网箱的容积损失率仅为18.4%,其弱点是会使得网箱阻力增加,对网箱锚泊系统的要求提高.研究的结果与目前为止的模型试验结果和在网箱方面的一般经验基本吻合,本研究方法基本上是合理可行的.     

美国大豆工业海洋网箱水产养殖技术近海海水鱼类养殖网箱工程技术手册(三十九)

(上接2012年第10期) X.沉没测试 1.概述 作为USB项目7515-在海湾建造和开发OCAT网箱(参阅Ⅷ章.OCAT设计评估和改进网箱的建造)的一部分,由New Hampshire大学制作和组装了一个海洋网箱养殖系统(OCAT).组装好以后此网箱和锚定系统在Great Bay Estuary,New Hampshire进行了开发,用了一周的时间对系统的拖曳力,水速的测量和网箱的沉没深度进行了测定.此研究的要达到的目的如下: ■用水流仪和负载传感器装配了OCAT系统和测试现场 ■ 在河流的出口处布置了网箱和锚定系统 ■ 检测了网箱内部和外部的水流速度 ■ 检查网箱的可沉没性 ■ 安装和测试水流偏转系统 UNH在他们递交给美国大豆工业协会为其USB项目7516"OCAT网箱的沉没测试(Celikkol et al,2007e)"的最终报告中记录了此项研究的结果.     

美国大豆工业海洋网箱水产养殖技术近海海水鱼类养殖网箱工程技术手册（四十四）

7．讨论 在水流中,安装了25ram条长网具的OCAT网箱系统沉没的深度没有条长40mm的网箱深。25mm条长类型和40mm条长网的最大位移分别为15．6米和-17.3米。虽然设计的网箱是可以沉没的,但是安装40mm条长网的网箱系统上的重物链碰到了海底。假如此系统被布放在流速较高的区域内,可能需要增加网箱框架内的浮力。     

方形箱网结构减流效果试验

根据降低流速对深水网箱养殖的影响这一需要,依据目前深水网箱的尺寸和渔具模型试验方法,设计并制作一个浮式箱网结构模型,同时进行水槽实验。实验在箱网的尾部设定一系列的断面和测量点,通过三维流速仪测量各点在不同实验流速下的流速,通过分析相关数据,探讨了该箱网减流结构尾部的流速分布和减流效果。实验流速采用了32.23 cm/s、50.19 cm/s、67.79 cm/s,分别相当于实际流速45.58 cm/s、70.79 cm/s、95.67 cm/s。实验测量了减流装置尾部减流区域50 cm到125 cm处的流速分布,相当于实际海域中距离减流装置尾部15 m到37.5 m处的流速分布。实验结果显示,箱网尾部的流速减小区域是在网箱网袋与来流垂直的投影面上,减流百分比在20%～45%左右,而箱网两侧的流速略有增加。从实验结果来看,这一结构能有效减小流速,通过合理的设计和在海域中布设,能够满足深水网箱养殖的减流需要。     

歧管式高压射流水下洗网机的设计

文章针对深水网箱养殖过程中岸电供应不便而给网衣的水下清洗带来极大困难的问题,研制了歧管式高压射流水下洗网机,克服了高压仓式洗网机水头损失大的缺点。通过水力学计算得到歧管式高压射流水下洗网机射流压力P=5．57MPa、喷嘴孔径d=2．6mm、射流速度v=104．1m·s。和射流功率P=12．3kW、射流反冲力F=234．96N。水下洗网机的海上清洗试验表明,在工作泵满足工作压力和设计流量条件下,歧管式高压水射流水下洗网机的综合性能达到了设计要求。     

基于实时水质参数的智能养殖装备设计

针对现有水产设备机械化和自动化程度较低,增氧机作用范围有限和投饲机无法自适应投饲的问题,研究设计了一种新型的基于实时水质参数的智能养殖装备。该装备硬件上利用传感器对水质参数进行实时监测,采用太阳能与交流电源混合供电。其中,移动式太阳能增氧机使用超声波测距进行避障,可随机行走、增大增氧机的工作范围;太阳能智能投饲机使用称重传感器进行饲料称重,以实现精确定量投饲。该装备软件上支持个人计算机和手机等多个平台客户端,实现实时水质参数查询、远程增氧、远程投饲、远程智能控制等功能。池塘应用试验结果表明,该装备的监测水质数据可信度高,实时通讯丢包率低于0.2%,在保证增氧能力的情况下,增氧机作用范围比传统水车式增氧机提高10%;能够在良好的水质环境中完成精确定量投饲。研究表明,该装备的应用有助于推进水产设备智能化、自动化的发展,实现节能降耗、绿色环保的目标。     

深水区大型抗风浪网箱配套设施系统

本文分析深水抗风浪网箱的发展现状,阐述网箱配套设施的基本工作原理,并提出装备网箱配套设施的必要性.为使深水抗风浪网箱养殖业稳步、持续发展,必须加大科研投入,尽快开展网箱配套设施的研究,研发一批实用性强、生产效率高、节省劳力和减轻劳动强度的设备.     

波浪作用下半潜式养殖网箱水动力特性

半潜式深远海养殖网箱在波浪作用下会发生变形与运动。为保证网箱结构的稳定性,需对其水动力特性进行分析。本研究基于有限元法建立了波浪作用下一种半潜式网箱的数值模型,通过仿真计算求解网箱的锚绳受力与运动情况。首先,将计算机模拟值与物理水槽试验值进行比较,验证数值模型的准确性。然后,分别研究了半潜式网箱在3种压载状态下的动力响应情况,分析比较了不同波浪条件下网箱锚绳张力、垂荡、纵荡和纵摇的计算结果。结果显示,计算值与试验值基本吻合,二者的相对误差在5%左右。当波高一定时,网箱迎浪侧和背浪侧锚绳受力与波浪周期改变无明显关联;当周期一定时,两侧锚绳受力均随波高的增加而增大。网箱的垂荡、纵荡及纵摇值均与波高呈正相关,随着半潜式网箱吃水的增加,网箱的垂荡、纵荡及纵摇值基本呈减小趋势。网箱在3种压载状态下最大垂荡值和纵荡值分别为12.67 m和10.59 m,网箱在空载状态下的最大纵摇值≤15°,表明半潜式网箱结构具有较好的稳定性。研究结果可为我国深远海养殖网箱设计提供理论参考。     

Evaluation of floating cages as an experimental tool for marine shrimp culture studies under practical earthen pond conditions

The New Caledonia blue shrimp Litopenaeus stylirostris is commercially produced under semi-intensive rearing conditions. The size of the farming earthen ponds (5–10 ha) and the subsequent production constraints make it difficult to use them as experimental units for random experiments. Moreover, since every pond has its own characteristics, ponds' effects cannot be ruled out, thus making it hard to define true replicates.In order to design future experiments under conditions resembling those used in production, we evaluated the possible use of floating cages as experimental units with the aim of assessing treatment effects with a reasonable statistical power. To this end, two sets of floating cages were placed respectively in two different ponds in a commercial farm. In both cases the zootechnical conditions in the cages were similar in post-larvae origin, management, and diet and feeding regime.The aim of the study was to evaluate on a technical basis the possibility of rearing shrimps in floating cages set up in earthen ponds and to assess this method from a statistical standpoint. Shrimps reared in and outside the cages showed comparable growth and survival rates. The variability in the zootechnical parameters between cages, expressed as the estimated coefficient of variation (CV) for survival rate, total final biomass (g), final body weight (g), daily increment in body weight (g day^− 1) and FCR were 11.0, 13.7, 4.4, 5.4, and 7.0%, respectively. On the basis of these figures, we calculated for a given statistical power (80%) the number of replicates (cages) that would be required to reveal significant differences between two treatments, at a 5% level of significance. We found that for expected differences of 20% from the control mean, 3 and 6 floating cages per treatment would be reasonable to determine statistical differences for growth parameters and survival rate, respectively. Moreover, we showed a significant pond effect in regard to survival and growth between the two sets of cages. These results illustrated the within-farm variability among the ponds, and confirmed that the specific characteristics of each pond from the same farm make it difficult to use the ponds themselves as experimental units.The study demonstrates that rearing in floating cages is an economical, powerful and sensitive experimental tool for shrimp culture studies specifically carried out under conditions close to semi-intensive production.     

潜浮式船型桁架结构深海养殖网箱避浪性能研究

深海网箱作为现代海洋渔业拓展外海养殖空间的重要养殖装备，其布设环境一般较近海更为复杂恶劣，对于保障其安全性和稳定性提出了更高的要求。本研究针对一种单点系泊潜浮式船型桁架网箱开展了模型比尺为1︰40的波浪流水池试验，重点围绕该网箱在不同吃水深度受波浪作用的系泊受力、升沉、纵摇和横摇等水动力学特性进行了比较分析。试验结果显示，波高为7.5~12.5 cm时(原型3~5 m)，网箱漂浮状态即可以满足养殖需求，其系泊力及运动响应均较小，具备较高的安全性和稳定性；恶劣海况时，即本试验中波高为15.0和17.5 cm (原型6 m和7 m)，通过整体下潜的方式网箱具有良好的避浪性能，其中，系泊力减幅达70%以上，升沉、纵摇和横摇等运动分量减幅也达20%~60%；波流试验中，海流对网箱避浪性能存在一定的影响，但总体上仍然具有较好的避浪效果。研究结果可为单点系泊潜浮式深海网箱的安全运行与日常管理提供理论依据和数据参考。     

鱼松片加工工艺优化及成型设备研究

以风干鲢鱼为原料,开发了鱼松片加工工艺:经高压蒸煮、打击成绒、压制成型、干燥等工序后,制成即食型的方便食品鱼松片.通过正交试验以感官品质评定为指标,得到了鱼松片成型的最优工艺:糕粉添加量为20％,成型压力为3 MPa,保压时间为20 s.为满足工艺条件和工业化生产的需要,设计了自动化程度高的鱼松片成型机,介绍了其基本结构、工作原理及主要技术参数.     

Technological solutions and operational measures to prevent escapes of Atlantic cod (Gadus morhua) from sea cages

Escapes of cod (Gadus morhua) from sea cages represent an economic problem for farmers and a potential environmental problem. We estimate that 0–6% of cod held in sea‐cage farms in Norway were reported to have escaped each year from 2000 to 2005, which is a high proportion compared with salmon. We interviewed employees at 19 coastal sea‐cage cod farms in Norway to investigate both how and why cultured cod escape and to document cage handling and management strategies that were effective in minimizing escapes. Based on the interviews, we describe five working hypotheses that may explain why a greater proportion of cod than salmon escape: (1) cod are more willing to escape than salmon; (2) cod bite the net cage and create wear and tear; (3) net cages have insufficient technical standards for cod culture; (4) cod are placed in sea cages at considerably smaller sizes than salmon; and (5) cod are more popular feed for predators. Preliminary testing of the hypothesis that cod bite netting and create holes was done by placing pre‐damaged net panels with cut twines and control panels inside sea cages. Holes in the pre‐damaged net panels increased in size over a period of 3 months. The type of damage indicated that biting of netting twines was the likely cause.     

Automatic Bluefin Tuna (Thunnus thynnus) biomass estimation during transfers using acoustic and computer vision techniques

In this work, acoustic and computer vision techniques are combined to develop an automatic procedure for biomass estimation of tuna during transfers. A side scan sonar working at 200 kHz and a stereo camera, positioned facing towards the surface to record the ventral aspect of fish, are set as acquisition equipment. Moreover, a floating structure has been devised to place the sensors between cages in transfers, creating a transfer canal that allows data acquisition while fish swim from donor to receiving cage. Biomass assessment is computed by counting transferred tuna and sizing a representative sample of the stock. The number of transferred tuna is automatically deduced from acoustic echograms by means of image processing techniques, whereas tuna size is computed from the stereo videos using our automatic computer vision procedure based on a deformable model of the fish ventral silhouette. The results show that the system achieves automatic tuna counting with error below 10%, achieving around 1% error in the best configuration, and automatic tuna sizing of more than 20% of the stock, with highly accurate Snout Fork Length estimation when compared to true data from harvests. These results fulfil the requirements imposed by International Commission for the Conservation of Atlantic Tunas for compliant transfer operations.     

Numerical analysis of the effects of gas-phase properties on the internal characteristics and wear in a centrifugal pump

Centrifugal pumps are indispensable in aquaculture engineering. The existence of bubbles is inevitable in a centrifugal pump and may affect the performance of the pump which delivers solid-liquid two-phase flow. Thus, this study aims to analyze the effects of gas-phase properties on the internal characteristics of a centrifugal pump by using a computational fluid dynamic code based on Eulerian multiphase mode and a standard k–ε two-equation turbulence model. Results show that gas-phase properties, such as concentration and diameter, affect the absolute pressure and the phase distribution in the centrifugal pump. The gas-phase distribution on the working faces of blades is greater than forces on the back face of the blades. The larger the diameter of the gas-phase is, the easier it is to be concentrated; Thus, the working face of the blades is prone to cavitation and corrosion, and with the increase of the bubble size, the cavitation corrosion of the back surface of the impeller becomes more serious. The solid-phase velocity and static pressure distribution increase with increasing concentration or diameter of gas-phase. The solid-phase is more easily leave the impeller area and enter the volute because of the existence of gas-phase, which may lead to abrasion of volute. The existence of gas makes the solid velocity distribution in the centrifugal pump more uneven, which may cause uneven wear of the centrifugal pump. The obtained results by this method can reveal the effects of gas-phase properties and wear on the internal characteristics in centrifugal pumps and are helpful for improvement and empirical correction in the hydraulic design of centrifugal pumps.