A model experiment on the pair midwater trawl net applicable to 800 PS class Korean pair bottom trawlers was carried out in the special-prepared experimental thank. the tank was prepared as a reverse trapezoid shape in its vertical section by digging out flat soil. The dimension of the tank showed the 9.6 W×43.0 L(m) of the upper fringe and the 4.8 W×38.0 L(m) of the bottom with 3.0m in depth. The depth of water was maintained 2.7m during experiment. The model net was prepared based on the Tauti's similarity law of fishing gear in 1/30 scale considering the dimension of the experimental tank. Mouth performance of the model net during towing were determined by the photographs taken in front of the net mouth with the combinations of towing velocity, warp length and distance between paired boats. The results obtained can be summarized as follows: 1. Vertical opening of the model nets A and B was varied in the range of 0.18~0.88 m and 0.21~0.78 m (which can be converted into 5.4~26.4m and 6.3~23.4 m in the full-scale net) respectively, and was varied predominantly by towing speed. Vertical opening (H which is appendixed m for the model net. f for the full-scale net. A and B for the types of the model net) can be expressed as the function of towing velocity〈TEA〉Vtas in the model net 〈TEA〉〈/TEX〉Vt〈/TEX〉 : m/ sec)〈TEA〉HmA=1.67〈TEA〉〈/TEX〉e-1.65Vt〈/TEX〉 〈TEA〉HmB=1.15〈TEA〉〈/TEX〉e-1.13Vt〈/TEX〉, in the full-scale net (〈TEA〉Vt : k't) 〈TEA〉〈/TEX〉HfA〈/TEX〉=50.27〈TEA〉e-0.37Vt 〈TEA〉〈/TEX〉HfB〈/TEX〉=34.46〈TEA〉e-0.26Vt. 2. Horizontal opening of the model nets An and b was varied in the range of 1.03~1.54m and 1.04~1.55 m (which can be converted into 30.9~46.2 m and 31.2~46.5m in the full-scale net) respectively, and was varied predominantly by distance between paired boats. Horizontal opening (W, appendixes are as same as the former) an be expressed as the function of distance between paired boats 〈TEA〉〈/TEX〉Db〈/TEX〉as in the model net 〈TEA〉WmA=0.69+0.09〈TEA〉〈/TEX〉Db〈/TEX〉 〈TEA〉WmB=0.73+0.09〈TEA〉〈/TEX〉Db〈/TEX〉, in the full-scale net 〈TEA〉WfA=20.81+0.09〈TEA〉〈/TEX〉Db〈/TEX〉 〈TEA〉WfB=22.11+0.09〈TEA〉〈/TEX〉Db〈/TEX〉 3. Net opening area of the model net A and B was varied in the range of 0.28~1.04 〈TEA〉m2 and 0.33~0.94〈TEA〉〈/TEX〉m2〈/TEX〉(which can be converted into 252~936〈TEA〉m2 and 297~846〈TEA〉〈/TEX〉m2〈/TEX〉 in the full-scale net) respectively, and was varied predominantly by towing velocity. Net opening area (〈TEA〉S, appendixes are as same as the former) van be expressed as the function of towing velocity〈TEA〉〈/TEX〉Vt〈/TEX〉 as in the model net 〈TEA〉vt : m/sec) 〈TEA〉〈/TEX〉SMa〈/TEX〉=2.01〈TEA〉e-1.54VT 〈TEA〉〈/TEX〉SmA〈/TEX〉=1.40〈TEA〉e-1.65Vt, in the full-scale net (〈TEA〉Vt : k't) 〈TEA〉〈/TEX〉SfA〈/TEX〉=1.807〈TEA〉〈/TEX〉e-0.35Vt〈/TEX〉 〈TEA〉SfA=1.265〈TEA〉〈/TEX〉e-0.24Vt〈/TEX〉. 4. Filtering volume of the model nets A and B was varied in the range of 0.32~0.55 〈TEA〉m3 and 0.37~0.55〈TEA〉〈/TEX〉m3〈/TEX〉(which can be converted into 8.640~14.850 〈TEA〉m3 and 9.990~14.850〈TEA〉〈/TEX〉m3〈/TEX〉in the full~scale net) respectively, and was predominantly varied by towing speed. filteri..

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