【摘要】 针对在中东大西洋海域作业的远洋中型单拖渔船缺乏捕捞小型中上层鱼类手段的现状，该研究通过分析大型中层拖网和中国近海大网目拖网的结构特点和水动力参数，综合大型中层拖网和近海大网目拖网的设计参数，优化设计了网口网目尺寸为12 m、网口周长分别为552、456和360 m共3个规格的试验网，并进行模型试验和海上生产试验。结果表明：在拖速为2.31m/s时，模型试验测得552型试验网（网口周长552m）在L/S袖端间距L与长纲长度S之比为0.35、0.40、0.45 3种水平下的平均阻力为151.82 kN，网口高度为28.74 m;456型（网口周长456 m）的平均阻力为135.60 kN，网口高度为24.96 m;360型（网口周长360 m）的平均阻力为70.76 kN，网口高度为20.20 m。试验船在中东大西洋海域生产试验时，552型试验网平均拖速为2.06 m/s，平均每小时产量为0.13 t,456型试验网平均拖速为2.26 m/s，平均每小时产量为0.77 t,360型试验网平均拖速为2.52 m/s，平均每小时产量为1.13 t。中型拖网渔船使用中层拖网捕捞游泳能力较强的小型中上层鱼类，需要较高的拖速，作业拖速为2.31～2.57 m/s时产量较好。试验网具部分（不计网板、曳纲）的功率消耗占主机额定功率的11%～16%。研究结果有助于设计适合中国远洋中型拖网渔船的中层拖网。更多还原

【Abstract】 Medium-sized single trawlers are still lacking to catch the pelagic fishes in the Eastern Central Atlantic Ocean in recent years. In this study, an optimal design and test were performed on the mid-water trawl for the medium stern trawler,according to the structural and hydrodynamic parameters of the current large mid-water and large-mesh offshore trawl. Three kinds of perimeters were set for the specification of net mouths in the model and offshore production, including 552, 456, and 360 m. Specifically, the mesh size of net mouth was 12 m, the length of body net/circumference net-mouth was 0.217 m, and the length of wing/circumference net-mouth was 0.076 m. The results show that the average resistance of type 552(Circumference net-mouth was 552 m) was 151.82 kN, and the height of net opening was 28.74 m; the average resistance of type 456(Circumference net-mouth was 456 m) was 135.6 k N and the height of net opening was 24.96 m; the average resistance of type 360(Circumference net-mouth was 360 m) was 70.76 kN and the height of net opening was 20.20 m, when the trawl speed was 2.31 m/s, while, three kinds of expansion ratio were 0.35, 0.40, and 0.45(wingtip space between/ground rope length L/S), respectively. A model test was also carried out in the Eastern Central Atlantic Ocean. It was found that the average yield per hour of type 552 was 0.13 t and the volume of filtered water per second was about 2442 m~3 when the trawl speed was 2.06 m/s. Nevertheless, only 5% of the pelagic fish was captured after the detection of pelagic fish flocks, indicating the very low net output. When the trawl speed was 2.26 m/s, the average yield per hour of type 456 was 0.77 t and the volume of filtered water per second was about 1927 m~3. When the trawl speed was 2.52 m/s, the average yield per hour of type 360 was 1.13 t and the volume of filtered water per second was about 1321 m~3. The maximum towing speed of type 360 reached 2.67 m/s, and the maximum output of single net trawl operation in 4 hours reached 20 t. Since type 360 presented the smallest net mouth and the water filtration volume per unit time, the output per unit time was much higher than that of the rest.Particularly, the mid-water trawls were adopted in the medium trawlers, in order to catch the small pelagic fish with better swimming ability, where the higher towing speed was required. Furthermore, a better yield was achieved, as the increase of the trawl speed in the range of 2.31-2.52 m/s. Once the mid-water trawl run a higher towing speed, the main engine of the fishing boat was consumed more power to overcome the fluid resistance. Therefore, the power consumption of the test net part(excluding otter board and warp) was recommended as 11%-16% of the rated power of the main engine, when the decreasing power was allocated to the net. In addition, the ultra-high molecular weight polyethylene(UHMWPE) fiber can be widely used to reduce the diameter and area of the test net, further reducing the resistance for the better performance of the test net. The finding can provide an important reference for the structural design and optimization of the mid-water trawl in the medium stern trawler on ocean fishing.更多还原