基于海上实测和模型试验的南极磷虾中层拖网性能分析

发布时间：2018-06-11 13:53

本文选题：南极磷虾 + 拖网性能　；参考：《上海海洋大学》2017年硕士论文

【摘要】：南极磷虾(Euphausia superba)分类上属于甲壳类浮游动物,广泛分布于环南极大陆架水域,是地球上已知的生物量最大的单种生物,且其体内具有人类全部所需的氨基酸,因具极大的潜在开发利用价值而备受世界各国的关注。单船中层拖网是捕捞磷虾的主要作业方式,我国捕捞渔船使用的磷虾拖网也从2009年的大网目磷虾拖网改进为小网目磷虾拖网。和大网目拖网相比,小网目拖网规格相对较小,作业时不会出现如大网目拖网那样的相互缠绕,操作较为方便简单,起、放网也较节省时间。作者曾于2015年和2016年随我国南极磷虾捕捞渔船赴南极执行农业部南极海洋生物开发专项相关调查工作,认为我国南极磷虾捕捞渔船目前使用小网目磷虾拖网在海上捕捞作业过程中还存在一些问题,需要展开研究:(1)如何确定网位水层与拖速和曳纲长度的变化,找出其规律。(2)南极磷虾具有昼夜垂直移动习性,使得网位的控制有一定的难度,需要通过控制浮沉比配备的同时,还需要知道如何配置重锤的重量才能使得能达到某一水层且网具性能会发生怎样的变化?循环水槽试验中无法对于重锤影响水层的研究,本章主要是研究重锤对网具性能的影响。(3)网板的扩张性能与网具的配置关系,网具阻力在整个拖曳系统占据怎样的地位?对于海上使用的网板按照田内准则制作模型网板,通过拖曳水槽研究网板的阻力与曳纲和速度的变化以及网板在拖网系统中阻力分配情况。(4)南极磷虾拖网内衬网网衣较多,且内衬网网目较小,虽然捕捞产量效果较为理想,但阻力较大可能会使得能耗会增大。因此,内衬网的线面积对网具性能的影响也是值得研究的问题。(5)完成模型试验后对比海上实际测量的网具阻力和网口高度的变化与拖速和曳纲长度的关系,研究海上实测和模型试验的南极磷虾拖网性能。上述(1)的问题和下述(1)的试验结果是基于作者于2015年2月-7月在青岛远洋捕捞有限公司“明开轮”在南极执行项目时海上拖网试验收集的数据,通过研究分析得出网位变动与拖速和曳纲间的关系,试验网记为1号拖网。上述(2)、(3)、(4)、(5)四项研究的问题和下述(2)、(3)、(4)、(5)的试验结果均是基于作者于2016年1月至5月在中国水产有限公司“龙腾轮”的执行南极磷虾项目时,对渔船所使用的拖网完成实际海上测试后发现的一些主要问题,并通过模型试验研究得出的主要结果,试验网可记为2号拖网。本文通过海上实际生产时的拖网捕捞数据,结合东京海洋大学循环水槽和日本水产工学研究所拖曳水槽模型试验,得到的主要结果如下:(1)南极磷虾拖网(Net 1)的网位变化主要由曳纲长度决定,曳纲每增加20 m,网位深度平均下降约1.9 m,曳纲长度对磷虾拖网网位的影响极显著(p0.01)。拖速由低速(1.0 Kn)增至高速(3.0 Kn)时,网位平均上升速率约2.9m/Kn,网口高度平均降低19.8%。拖速对网位和网口高度的影响显著(p0.05)。网位调节至稳定状态需要一定时间,一般平均需要3 min。(2)拖网袖端水平扩张与下纲长度之比(L/S)的改变导致网具阻力的变化幅度较小,而改变拖速时网具阻力的变化幅度较大。水平扩张比(L/S)和拖速对网具阻力、网口高度均存在显著影响(p0.05)。在不同水平扩张下,拖速从1.5 Kn增加到3.5 Kn时,网具阻力平均增大41.19%,且随着拖速的增大,网具阻力的增大幅度减小;随着水平扩张的增大,尽管网具阻力的增大幅度也随之增大,但增大幅度不大,平均不到1%(0.925%)。在拖速分别为1.5 Kn、2.0 Kn和2.5 Kn时,网口最优形状均为L/S=0.55时;拖速为3.0 Kn和3.5 Kn时,网口最优形状均为L/S=0.40时,表明在较高速度拖曳时,对网口的水平扩张要求不需要太大。(3)改变重锤重量对网口高度、网具阻力和能耗系数的变化存在显著性影响(p0.05)。改变重锤重量主要是为了调节南极磷虾拖网的捕捞作业水层。实际生产时,船长一般根据磷虾栖息水层昼夜垂直移动的特点,白天和晚上均要调整重锤的重量。结果表明,配置300kg重锤时,网口高度提高了约3.08%(对比未加重锤),重锤重量从300 kg增加到600 kg,网口高度变化幅度较小,但是随着重锤重量的增加,拖网能耗系数降低,装配300 kg和600 kg重锤时的能耗系数变化曲线相差很小。故可认为,在保证网具能达到预设的水层时可以不需要配置过重的重锤以便起网时方便操作。(4)内衬网线面积的变化对网具阻力和网口高度具有极显著影响(p0.01)。随着拖速的增大,内衬网线面积的变化对网具阻力的变化幅度会增大,对应的能耗系数也呈现相同的规律。在低拖速(V≤2.0 Kn)和较低的水平扩张时,在保证磷虾不会通过网目挤压或逃逸的前提下,可考虑将内衬网的线面积比优化为16.93%,即由网身第四段开始附加内衬网会更有利于捕捞效率的提高和降低能耗。(5)拖曳水槽试验的拖网阻力随拖速的变化在拖速低于2.5 Kn和海上实测拖网阻力基本相等,在拖速高于2.5 Kn时拖曳水槽试验的拖网阻力明显大于海上实测的拖网阻力,拖曳水槽试验的拖网阻力比海上实测的拖网阻力平均大8.76%,而通过循环水槽试验得出的网具阻力平均比拖曳水槽试验的拖网阻力大21.74%,比海上实测的拖网阻力平均大31.61%。虽然试验网板在低拖速(V≤2.0 Kn)时水平扩张很小,但在拖速超过2.0 Kn时网口扩张还是可以满足磷虾拖网作业特性的。当然为了能够保证在低拖速时网具也能达到较好的网形效果,对于低拖速,较大扩张的网板开发也是非常有意义的。因此,在接下来的拖网优化试验中,应该考虑将网具模型再变大,将主尺度缩小,扩大网板模型有利于对网板真是情况进行较好的了解和试验,降低模型失真带来的误差。通过在三种试验条件下的拖网阻力与拖速的关系拟合优化公式为:R=135.06V~(1.4706)(R~2=0.9099)。
[Abstract]:The Antarctic krill (Euphausia superba) belongs to the crustacean zooplankton, widely distributed in the waters of the Antarctic continental shelf. It is the largest single species known on the earth, and has all the amino acids needed in the human body. It has attracted much attention from all countries in the world because of its great potential value for exploitation and utilization. It is the main mode of fishing for krill, and the krill trawl used by fishing boats is also improved from the large mesh krill trawl in 2009 to the small mesh krill trawl. Compared with the big mesh trawl, the size of the small mesh trawl is relatively small, and the operation will not appear as a big mesh trawl. In 2015 and 2016, the author went to the Antarctic to carry out a special investigation on the Antarctic marine biological development of the Ministry of agriculture with the fishing boat of the Antarctic krill to the Antarctic in 2015 and 2016. It is considered that there are still some problems in the process of using the small krill fishing boat in the fishing operation of the small mesh krill trawling. (1) How to determine the change of the net position water layer and the change of the drag speed and the length of the traction class. (2) the Antarctic krill has a diurnal vertical movement habit, which makes the control of the network bit difficult. It needs to know how to configure the weight of the heavy hammer to reach a certain water layer and the performance of the net. How does life change? In the cycle test, there is no study on the impact of heavy hammer on the water layer. This chapter mainly studies the impact of the heavy hammer on the performance of the net gear. (3) the relationship between the expansion performance of the net plate and the configuration of the nets, and how the net resistance is occupied by the whole towing system? Through the towing sink to study the resistance of the net plate and the change of the drag and speed and the distribution of the resistance of the net plate in the trawl system. (4) the Antarctic krill trawl netting net clothing is more, and the net mesh net mesh is small. Although the fishing output is more ideal, the greater resistance may increase the energy consumption. Therefore, the line area of the inner lining net is the same. The effects of the performance of the nets are also worthy of study. (5) after completing the model test, the relationship between the resistance of the net and the height of the net and the length of the towing length of the mesh are compared, and the performance of the Antarctic krill trawl is studied. The problems mentioned above (1) and the results of the following (1) are based on the author's 2015 The data collected by the sea trawl test during the Qingdao ocean fishing Co., Ltd. in the -7 month of February, was collected by the trawl test in the Antarctic execution project. Through research and analysis, the relationship between the change of the net position and the drag speed and the drag class was obtained. The test network was recorded as No. 1 trawl. The above (2), (3), (4), (5) four research problems and the following (3), (4), (5) test results were all On the basis of the author's implementation of the Antarctic krill project from January 2016 to May, the main results of the trawl trawl used by the fishing vessel were found after the actual marine test was completed, and the main results obtained through the model test study could be recorded as 2 trawl. The main results are as follows: (1) the main results are as follows: (1) the network position of the Antarctic krill trawl (Net 1) is mainly determined by the length of the tracer, the traction is increased by 20 m, the depth of the net position decreases about 1.9 m, and the length of the tracer to the trawl net of the krill The effect is very significant (P0.01). When the tow speed is increased from low speed (1 Kn) to high speed (3 Kn), the average rise rate of the net position is about 2.9m/Kn, and the average decrease of the 19.8%. tow speed on the network position and the height of the net is significant (P0.05). The net position adjustment to the stable state needs a certain time, and the average need for the average 3 min. (2) trawl sleeve end horizontal expansion and the lower class The change of the length ratio (L/S) leads to a small change in the resistance of the net, and the change of the resistance of the net is larger. The horizontal expansion ratio (L/S) and the tow speed have significant effect on the net gear resistance and the net height (P0.05). When the drag speed increases from 1.5 Kn to 3.5 Kn, the drag of the net increases by 41.19%, and the drag speed increases by 41.19%. With the increase of the drag speed, the increase of the resistance is reduced, and with the increase of the horizontal expansion, the increase of the resistance of the net is increased, but the increase is not 1% (0.925%). The optimum shape of the net is L/S=0.55 when the tachow is 1.5 Kn, 2 Kn and 2.5 Kn, and the net mouth is optimal when the tow speed is 3 Kn and 3.5 Kn. When the shape is L/S=0.40, it is shown that the horizontal expansion of the mesh mouth is not needed too much at the high speed drag. (3) the change of the weight of the heavy hammer on the height of the net, the change of the resistance and the energy consumption coefficient (P0.05). The weight of the heavy hammer is mainly to adjust the fishing water layer of the Antarctic krill trawl. The captain generally adjusts the weight of the heavy hammer in the daytime and night according to the characteristics of the diurnal and night vertical movement of the krill habitat. The result shows that when the 300kg weight is configured, the height of the net mouth is about 3.08% (contrasted without weight), the weight of the heavy hammer increases from 300 kg to 600 kg, and the height of the net mouth is small, but as the weight of the heavy hammer increases, the trawler is trawling. The energy consumption coefficient is reduced, and the variation curve of the energy consumption coefficient of the assembly of 300 kg and 600 kg weight hammer is very small. Therefore, it can be considered that the heavy weight of the heavy hammer can be not needed to ensure the convenient operation when the net is able to reach the preset water layer. (4) the change of the net line area of the inner lining has a very significant influence on the resistance of the net and the height of the net (P0.01). With the increase of the trailing speed, the change amplitude of the net line area will increase, and the corresponding energy consumption coefficient also presents the same rule. At the low drag speed (V < 2 Kn) and the low level expansion, the line area ratio of the inner liner can be optimized to 16.93% under the premise that the krill will not be squeezed or escaped through the mesh. At the beginning of the fourth segment of the net, the additional inner lining will be more beneficial to the increase of fishing efficiency and reduce the energy consumption. (5) the drag of trawl in the trawl test is basically equal to the drag speed less than 2.5 Kn and the trawl resistance at sea, and the trawling resistance of the trawler test at the towing speed is higher than 2.5 Kn is obviously larger than the towing drag at sea. Net drag, trawl drag resistance of trawl test is 8.76% higher than that measured at sea, and the drag of the net is 21.74% higher than that of the towed tank test, which is higher than that of the towed water trough test. It is 31.61%. larger than the measured trawl resistance at sea, although the horizontal expansion of the test net plate is very small at low drag speed (V < 2 Kn). However, when the tow speed is more than 2 Kn, the expansion of the mesh can still satisfy the krill trawl performance. Of course, in order to ensure that the net can achieve better net effect at low drag speed, the development of the larger expanse is also very meaningful for low tow speed. Therefore, the net gear should be considered in the trawl optimization test. The model becomes larger, the main scale is reduced, and the expansion of the mesh model is beneficial to the better understanding and test of the net plate, and the error caused by the model distortion is reduced. The optimum formula is R=135.06V~ (1.4706) (R~2=0.9099) through the relationship between the drag of trawl and the drag speed under the three test conditions.
【学位授予单位】：上海海洋大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S972.13

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