학공치 표층예망어구 모형의 운동특성

Dynamic Characteristics for the Model of Horn Fish Hemiramphus Sajor Surface Pair Trawl Gear

학공치 표층예망어구에 대한 일련의 기초 연구로서 표층예망어구 쌍끌이용 어선 9.98톤과 6.67톤을 이용하여 해상실험을 실시했던 실물어구를 기준으로 하여 축척비를 1/40로 정하고 Tauti의 모형망 비교법칙에 따라 제작한 모형어구(그물의 뻗친 길이 1.2m, 뜸줄의 길이 1.3m, 발줄의 길이 1.0m, 뜸 2.5g, 발돌 0.86g)를 사용하여 수조실험을 실시하였다. 양선 간격과 예인속도 변화에 따른 표층예망어구의 장력을 측정하고 동시에 수중형상을 관측수로 상방과 측면에 디지털 카메라를 설치하여 촬영하고 망고와 그물입구의 폭 등을 측정하고 이것들을 이용하여 실물어구의 망구면적과 여과수량 등을 해석한 결과를 요약하면 다음과 같다. 1. 망고(Nh)와 예인속도(Vt)와는 Nh=$(2.39Db^{-0.62})$ $Vt^{-0.56}$, 그물입구의 폭 (Nw)과 예인속도와는 Nw=$(0.96Db^{0.62})Vt^{0.11}$의 관계식으로 나타낼 수 있다. 단, Db는 양선간격이다. 2. 그물어구의 장력(Nt)과 예인속도와는 Nt=106.94Vt+1.43의 관계식으로 나타낼 수 있는데, 표층예망어구는 예인속도 1.5Kont 이상에서 수면과 수평이 되는 수중형상을 보였다. 3. 망구면적 (Na)과 예인속도와는 Na=(2.28Db$^{0.37})Vt^{-0.45}, 여과수량(Fv)과 예인속도와의 관계는 Fv=$(69.9Db^{0.37})Vt^{0.55}$의 관계식으로 나타낼 수 있는데, 망구면적과 여과수량은 양선 간격 25m일 때 최대를 나타냈으나 양선 간격 20m일 때와는 그 차가 거의 없었으며 양선 간격 15m 이하와는 차가 크게 나타났다.

This study describes the analysis on the dynamic characteristics of model as a fundamental studies for the horn fish Hemiramphus sajor surface pair trawl gear. The model experiments were carried out in a flume tank by using model net for the horn fish surface par trawl gear. The model net was made to the scale of 1/40 by scaling down two surfce par trawl boats of 6.67 and 9.98 ton used for sea experiment in the coast of Jeju Island. Dimensions of the model net were 1.2m for stretch length of net, 1.3m for float line, 1.0m for sinker line, 2.5g for floats, and 0.86g for sinkers. Experiments were conducted in the observation channel of a flume tank with experimental equipments used to change the distance between paired boats and towing velocity. Motion of model net during towing was recorded by two sets of digital camera which were placed in the top and side of the model net. The leading coordinate of net height and net mouth width was captured by the photograph analysis system. Through the experiment, we obtained the following results: 1. The relationship between the net hight(Nh) and towing velocity(Vt) during towing was found to be Nh=(2.39Db-$^{0.62})Vt^{0.56}$ and the relationship between the net mouth width (Nw) and towing velocity during towing was Nw=(0.96Db^{0.62})Vt^{0.11}$, where Db is the distance between paired boats. 2. The relationship between the net tension(Nt) and towing velocity during towing was found to be Nt=106.94Vt+1.43 and the model net becomes parallel to the water surface at the towing velocity larger than 1.5 Knot. 3. The relationship between the net opening area(Na) and towing velocity during towing was found to be Na=(2.28Db0.37)Vt.-0.45, and the relationship between the filtering volume(Fv) and towing velocity during towing was Fv=(69.9Db$^{0.37})Vt^{0.55}$. The net opening area and filtering volume reach maximum value at the distance of 25m between paired boats.