심해 저층트롤망의 수중형상에 관한 모형실험
A model experiment on the underwater shape of deepsea bottom trawl net
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초록
북태평양 해산어장에 사용할 저층트롤그물의 역학적 특성을 파악하기 위하여 회류수조를 이용하여 모형어구 실험을 실시하였다. 수조 실험은 유속과 그물의 전개각 변화에 따른 그물의 유체저항과 형상변화를 측정하였으며, 그 실험값을 실물 어구의 값으로 해석하여 보았다. 그 결과는 다음과 같다. 그물의 전개각이 30°일 때 실험 유속을 0.31m/s에서 0.92m/s까지 증가할수록 그물의 유체저항은 0.5kgf에서 2.68kgf까지 증가하였으며, 그물모형의 유체저항은 식 와 같다. 일정한 전개각에서는 실험 유속이 증가하면 망고는 낮아지고, 망폭은 커지는 것으로 나타났고, 일정한 유속에서 전개각이 증가 하면 망고는 낮아지고 망폭은 증가 하는 것으로 나타났다. 그물의 전개각이 30°에서 유속 0.61m/s일 때 망구면적은 0.214㎡이며, 모형망의 망구면적은 식 와 같다. 그물의 전개각이 30°에서 망구의 여과량은 0.76m/s(실물유속 5kt's)일 때 0.139m3/s로 어획효율이 가장 높을 것으로 나타났다. 그물의 형상변화는 유속의 변화에 점진적인 선형변화를 보여주었으나, 날개그물의 앞부분의 주름이 발생하여 이를 개선할 필요가 있었다.
Abstract
A model experiment using circulation water channel was carried out to investigate the dynamic characteristics of bottom trawl net which can be used in sea mount of North Pacific. Hydrodynamic resistance and shape variation according to the flow velocity and angle of hand rope transformation for net were measured, and experimental value was analyzed as the value of full-scale bottom trawl net. The results summarized are as follows; At the 30° of angle of hand rope to net, hydrodynamic resistance varied from 0.5kgf to 2.68kgf as the flow velocity increased between 0.31m/s and 0.92m/s, and formula of hydrodynamic resistance for the model net was . At the fixed angle of hand rope, Net height was low and Net width was high according to the increase of flow velocity, and in addition, vertical opening was low and Net width was high by the increase of angle of hand rope at the fixed flow velocity. At the 30° of angle of hand rope to net, net opening area was 0.214㎡ as flow velocity was 0.61m/s, and formula of net opening area for the model net was . At the 30° of angle of hand rope to net, catch efficiency seemed to be highest as 0.139m3/s of filtering volume at the 0.76m/s(5kt's) of flow velocity. Shape variation of net showed the gradual laminar transform for the variation of flow velocity but there needed some improvements due to the occurrence of shortening at the ahead of wing net.
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