1056型中东大西洋小型中上层鱼类中层拖网和1040型智利竹筴鱼中层拖网性能比较

Comparison on the hydrodynamic performance of mid-water trawl 1056 type for catching small upper-middle-class fish in middle-east Atlantic and 1040 type mid-water trawl for catching Chilean jack mackerel

本文选取我国大型中层拖网渔船生产作业所使用的网口周长相近的2顶中层拖网进行模型试验,结果表明:网口周长1 056 m的1号网(中东大西洋小型中上层鱼类中层拖网)与网口周长1 040 m的2号网(智利竹筴鱼中层拖网),当拖速从1.80 m·s-1升高至2.83 m·s-1时,在下袖端间距分别为60 m、67 m、74 m三种水平扩张下,1号网的平均阻力从134.85k N上升为290.38 k N;2号网的平均阻力从151.75 k N上升为333.53 k N;1号网的平均网口高度从55.59 m下降为41.60 m;2号网的平均网口高度从59.58 m下降为46.77 m。本次试验,1号网的阻力平均值为209.59 k N,网口高度平均值为47.95 m,2号网的阻力平均值为238.88k N,网口高度平均值为52.61 m,2号网的平均阻力比1号网的平均阻力高12.26%,网口高度高8.86%。试验网具在结构、网具阻力、网口高度等方面存在较明显的差异,但从能耗系数的角度来看,二者的捕捞效率相当接近。

This paper presented the model tests of two mid-water trawls, which were used in fishing grounds in middle-east Atlantic by Chinese large mid-depth trawl vessels, with similar circumstance of net mouth. The results showed that： comparing No. 1 net with circumstance of 1056 m （mid-water trawl for catching small upper-middle-class fish in middle-east Atlantic） and No. 2 net with circumstance of 1040 m （mid-water trawl for catching Chilean jack mackerel） , when towing speed rose from 1.8 m＂ s-l to 2.83 m＂ s-1, the average drag of No. 1 net increased from 134.85 kN to 290.38 kN under three horizontal expansions while that of No. 2 increased from 151.75 kN to 333.53 kN; the net mouth height of No. 1 net decreased from 55.59 m to 41.60 m while that of No. 2 net decreased from 59.58 m to 46.77 m under three horizontal expansions. In this experiment, the mean drag and mouth height of No. 1 net was 209.59 kN and 47.95 m respectively, while that of No. 2 net was 23.88 kN and 52.61 m respectively, which indicateed that the average resistance of No. 2 net was 12.26% greater than that of No. 1, and the height of No. 2 net was 8.86% higher than that of No. 1 net. Obvious differences on structure and hydrodynamic performance were found between two experimental trawls, but in terms of energy consumption coefficient, the fishing efficiencies of two trawls were pretty close.