摘要
现有的多点系泊系统的复杂性及其暂无替代系泊方式是制约网箱养殖产业走向深远海的因素之一。借鉴单点系泊系统的优势,设计出一型可应用于往复流情况下的新型单锚腿系泊系统,通过计算和海域实测试验表明,该单锚腿系泊系统具备两级刚度的特点,满足网箱的系泊需求。在此基础上,以NACA0030对称翼形网箱为系泊对象,对单锚腿系泊系统与翼型网箱的耦合系统展开了南海海域50YRP海况下7个典型工况的扫略计算,完成系泊系统的安全与效用评估。结果表明,所设计的系泊系统在15~50 m水深范围内均具备较高的安全性,最适宜30 m水深使用。
Although deep water cage culture has developed well and rapidly during the past two decades, achieving safe marine aquaculture has always been the ultimate goal of the industry. The mooring system plays an important role in the safety of deep water cage culture. The radiant multi-point mooring method is mainly adopted to moor cages. However, the multi-point mooring has high construction requirements while the aquaculture industry lacks professional construction equipments. Furthermore, marine aquaculture requires the occupation of sea areas, and one way for farmers to pursue high economic profits is to arrange as many cages as possible in a given sea area. Nevertheless, the radiant multi-point mooring method tends to occupy more sea areas due to the requirements of safe mooring radius. The deeper the water depth is, the larger the occupied area is, creating contradiction between these two aspects. Therefore, the development of cage culture towards deep sea has been restricted. This study designs a single anchor leg mooring system(SALMS) specifically for the cage industry, in an attempt to solve the problems and contradictions. We combined the characteristics of typical single point mooring systems in ocean engineering, especially the single anchor leg single point mooring system and the soft yoke single point mooring system. Then the designed mooring system was combined with the culture cage to establish a coupling analysis model. The top excitation of the mooring line, the displacement distance of the buoy and the tension changes of the floating cable were studied based on the model. The security of the mooring system, the utilization of the sea area and the applicability of the designed mooring system were further evaluated. In this study, a numerical simulation model was constructed with the commercial software OrcaFlex to simulate the force and dynamic behavior of the mooring system in waves and currents. The software was developed based on cable dynamics and can be used to simulate many types of marine structures. The designed mooring system consisted of a surface buoy, two underwater weights, an anchor, three segments of anchor chain and floating rope, which were modeled and combined by software-provided vessel, three degrees of freedom buoys, fix point and line units. For the vessel representing the surface buoy in the mooring system, the calculation of the hydrodynamic coefficient was done with the panel method of three-dimensional potential flow theory. To validate the numerical model, we not only organized physical experiment at sea area for the mooring system’s stiffness, but also considered a case based on the force of the net cage under steady water flow, from which we calculated and compared them with the simulated results. The results indicated a good agreement, proving that this type of mooring system had two levels of stiffness. Subsequently, the numerical model was used to simulate the force and deformation of the designed SALMS. The mooring object was the NACA0030 symmetrical airfoil cage, which was constructed specifically for single point mooring systems and occupied a sea area of 127.33 m2. Calculation was carried out for 7 typical conditions based on the environmental conditions of 50 YRP in the cultured sea area(using JONESWAP wave spectrum, peak increase factor was 1, significant wave height 2.93 meters, cross-zero period 8.01 seconds, and current velocity 1.5 m·s-1.). Multiple wave seed conditions’ calculation and extreme value analysis were carried out by considering both tensions of the anchor chain and the floating rope at connection point to the surface buoy, as well as the distance of the buoy from the equilibrium position. The results showed that the mooring system would deform under the action of various working conditions. The tension in the anchor chain under three working conditions at the same direction was greater than that under the other four kinds of non-co-directional conditions. The extreme tension values under three co-directional conditions increased with the increase of the angle value, and the load of the anchor chain reached the maximum under the working condition of 90° wave direction and 90° flow direction, which was 53.33 kN. The offset distance of the buoy to balance position was also the largest under this condition, being 8.99 m. Moreover, it was more reasonable to adopt the extreme value analysis method for safety check than the calculation of multiple wave seed conditions, verifying that the designed mooring system had high security and could promote the usage of sea area. Finally, through calculation and analysis of the forces under different water depths(15, 20, 30, 40, 50 m) and different floating rope lengths(10, 16, 24, 30, 36 m), we found that the mooring system could be safely used for water depths of 15 m to 50 m. It showed that the designed mooring system had wide applicability and was most suitable for 30 m water depth. Under certain conditions of water depth, the force of the floating rope decreased with the increase of the length. We recommend determining the length according to actual needs.
作者
王绍敏
袁太平
陶启友
郭杰进
胡昱
刘海阳
黄小华
WANG Shao-min;YUAN Tai-ping;TAO Qi-you;GUO Jie-jin;HU Yu;LIU Hai-yang;HUANG Xiao-hua(Key Laboratory of Open-Sea Fishery Development,Ministry of Agriculture,South China Sea Fisheries Research Institute,Chinese Academy of Fishery Sciences,Guangdong Cage Engineering Research Center,Guangzhou 510300,China)
出处
《海洋渔业》
CSCD
北大核心
2019年第6期725-735,共11页
Marine Fisheries
基金
广东省自然科学基金项目(2015A030313857)
国家自然科学基金项目(31772897,31402349)
中国水产科学研究院基本科研业务费资助(2017HY-ZD0604)
关键词
往复流
单锚腿系泊系统
深水网箱
海域实测
翼形
reciprocating water flow
SALMS
deep water cage
physical experiment at sea
airfoil
