漂浮状态下重力式及碟形网箱锚绳受力特性的比较

This paper focused on the force characteristics of mooring lines of the common used gravity cage and sea station cage under floating status. In this experiment, total four cage models were designed which included two gravity cage models, one sea station cage model and one quasi-sea station cage model. The gravity cages were made of the same materials but with different weighting system configurations. The sea station cage model and the quasi-sea station cage model were of the same diameter but the latter is 1.4 times in cage height to the former one which attributed greatly to the amplification of effective aquaculture volume up to 2.2 times. Four mooring lines were attached to each cage model on one side and the other side fixed on the bottom of the wave-current tank. Several kinds of experiment conditions were set, including pure current conditions, pure wave conditions and combined wave-current conditions. Forces were measured by four transducers attached to the bottom of the mooring lines respectively. Analysis was based on the resultant forces of the two current-ward or wave-ward mooring lines. Results from this study were presented and statically analyzed revealing that the quasi-sea station cage model suffered from greater forces compared with the other two kinds of cage models, which was more apparent under pure current conditions. It was interesting to find that the mass of the weighting system turned out to be relatively small effect on the forces acting on the gravity cage models under most conditions. Under pure wave conditions, several results of the forces acting on the gravity cage with heavier weighting system configuration were even smaller than those with lighter weighting system configuration. Conclusions were drawn that it was feasible to increase the mass of the weighting system properly to reduce the deformation of the netting system since it will not increase the forces acting on the gravity cages apparently. But it should be kept in mind that the operation of the cage will be affected directly by increasing the mass of the weighting system. As to sea station cage model, given the similar maximum aquaculture volume, results showed that the forces acting on it were approximately the same with that of gravity cages under the same conditions. But its huge size would lead to bad operation directly. Thus, when considering the force characteristics, the performance and management of the cages together with the cage prices, the co-authors recommended that gravity cages were more suitable currently as deep-water aquaculture facilities in China.

重力式与碟形网箱的锚绳受力特性比较

针对常见的重力式、碟形和拟碟形网箱在不同下潜深度状态下的锚绳受力特性进行了试验研究。试验共设模型4组,分别在纯流、纯波以及波流联合条件下进行。测力通过系缚于锚绳底端的4个拉力传感器获得。试验结果表明水流作用力的大小在很大程度上受网箱结构形式的影响,而在波浪条件下其影响相对较小。重力式网箱的配重形式及下潜形式对网箱的受力具有重要影响。另外,网箱在波流组合条件下的受力并不是纯流及纯波单独作用下的简单叠加。最后,在综合比较网箱价格和性能的前提下,对网箱结构形式的选择进行了一些讨论,并提出若干建议。

飞碟型网箱水动力模型试验与理论计算比较

通过飞碟型网箱模型试验,得出网箱水阻力和网箱网形的变化与流速之间的关系。网箱总阻力与箱体网衣湿水面积成正比,正常工作环境下网箱水阻力与流速之间成F=36090×V1.7904的关系。理论计算值一般比模型试验所得的网箱水阻力小10%左右。随着流速增加,网箱立柱向前倾斜的程度略为增加,当水流达到2kn时,其倾斜角约为5°。模型试验中,网箱网衣在不同的流速下变形不大,网箱容积基本保持不变。

不同张纲连接系统对碟形网箱浮环安全性能影响的分析

以碟形网箱浮环上的法兰所承受的剪应力来衡量浮环的安全性能。指出了法兰最危险的受剪情况,通过对网箱的力学分析和计算,分别得出单张纲和双张纲连接系统中法兰所受剪应力的理论计算公式。对目前应用的12边形碟形网箱进行了计算,得出法兰两端面所受剪应力在单张纲连接系统中同为5.74×107N/m2,在双张纲连接系统中(γ=45°)则分别为4.82×107N/m2和7.50×106N/m2,相比单张纲连接系统减小了16%和87%,从而说明了双张纲连接方式的优点。讨论结果表明,在双张纲连接系统中,12边形碟形网箱的γ应在0°-60°间选择为宜,且当γ=26°时,浮环的安全性能达到最佳。建议将常用的单张纲连接系统改进为双张纲式,以提高网箱的抗风浪性能。

浪流联合作用下碟形网箱单缆失效动力学分析

深海网箱长期放置于水文条件较为复杂的深海水域,研究网箱在复杂水域的水动力特性,对于网箱能否正常工作意义重大。通过采用国际先进的海洋工程软件OrcaFlex,以碟形网箱为例建立仿真模型进行动力学分析,通过对比网箱在浪流联合作用下,以及单缆失效条件下的动力学分析。得出了网箱在单缆失效状态下的系泊性能,为网箱系泊系统的设计制造提出优化意见。

碟形网箱水动力特性的研究

根据物模实验得到碟形网箱在不同海况条件下的受力并给出了其估算方法和公式及其相关系数的取值,同时总结了碟形网箱的运动特性。

不同系泊缆失效模式下深海碟形网箱的水动力特性

【目的】研究碟形网箱在系泊缆断裂的部位和数量不同时,系泊缆断裂后碟形网箱的水动力特性。【方法】结合某碟形网箱具体参数和其系泊系统布局情况,建立该碟形网箱的水动力分析模型,探究系泊缆在不同位置发生断裂和不同数量系泊缆断裂失效模式对碟形网箱水动力特性的影响。【结果与结论】1)不管何种模式的缆失效,都会导致其余未发生断裂系泊缆所承受的系泊张力重新分布。2)缆失效位置和数量的不同都会对网箱主体的六自由度运动产生不同的影响:当系泊缆锚固端断裂时,缆的自重及缆承受的水中阻力会对碟形网箱主体倾覆运动起到某种程度的限制作用。当系泊缆在上端断裂时,断裂后整根系泊缆完全脱离碟形网箱主体,如果自顶端断裂的系泊缆较多,就会导致碟形网箱主体发生大倾角倾覆;如果只剩下一根系泊缆与碟形网箱相连,碟形网箱有可能发生风标效应。