논문 상세보기
pp.196-205
종횡비, 다각형 모양에 따른 평판과 범포의 유체역학적 특성을 규명하고자 직사각형, 사다리꼴 모양으로 모형 평판과 범포를 제작하고 회류수조에서 양 · 항력 실험을 수행하였다. 그 결과를 요약하면 다음과 같다. 1. 직사각형 평판의 경우, 종횡비가 1 이하인 모형에서는 영각 40~42˚에서 최대 CL이 1.46~1.54, 1.5 이상인 모형에서는 20~22˚에서 10.7~1.11 정도였다. 직사각형 범포의 경우, 종횡비가 1 이하인 모형에서는 영각 32~40˚에서 최대 CL이 1.75~1.91, 1.5 이상인 모형에서는 18~22˚에서 1.248~1.40 정도였다. 같은 직사각형 모형에서는 범포가 평판보다 CL은 크게, 양항비는 작게 나타났다. 2. 사다리꼴 범포의 경우, 종횡비가 1.5 이하인 모형에서는 영각 34~44˚에서 최대 CL이 1.65~1.89, 2인 모형에서는 14~48˚에서 CL이 약 1.00 전후였다. 역사다리꼴 범포의 경우, 종횡비가 1.5 이하인 모형에서는 영각 24~36˚에서 최대 CL이 1.57~1.74, 2인 모형에서는 18˚에서 1.21이었다. 같은 사다리꼴 범포 모형에서는 전자의 모형이 후자보다 CL은 조금 크게, 양항비는 작게 나타났다. 3. 모형에서 물의 유체력을 많이 받을 수 있는 곳에서 만곡꼭지점이 만들어지며, 직사각형, 사다리꼴 모형에서는 종횡비가 클수록, 역사다리꼴 모형에서는 종횡비가 클수록, 역사다리꼴 모형에서는 작을수록 만곡꼭지점의 위치도 컸다. 4. 만곡도는 전 모형에서 종횡비가 클수록 컸으며, 직사각형, 사다리꼴 모형에서 영각의 클수록 컸고 직사각형 모형이 사다리꼴 모형보다 컸다.
As far as an opening device of fishing gears is concerned, applications of a kite are under development around the world. The typical examples are found in the opening device of the stow net on anchor and the buoyancy material of the trawl. While the stow net on anchor has proved its capability for the past 20 years, the trawl has not been wildly used since it has been first introduced for the commercial use only without sufficient studies and thus has revealed many drawbacks. Therefore, the fundamental hydrodynamics of the kite itself need to ne studied further. Models of plate and canvas kite were deployed in the circulating water tank for the mechanical test. For this situation lift and drag tests were performed considering a change in the shape of objects, which resulted in a different aspect ratio of rectangle and trapezoid. The results obtained from the above approaches are summarized as follows, where aspect ratio, attack angle, lift coefficient and maximum lift coefficient are denoted as A, B, CL and CLmax respectively : 1. Given the rectangular plate, CLmax was produced as 1.46~1.54 with A≤1 and 40˚≤B≤42˚. And when A≥1.5 and 20˚≤B≤22˚, CLmax was 10.7~1.11. Given the rectangular canvas, CLmax was 1.75~1.91 with A≤1 and 32˚≤B≤40˚. And when A≥1.5 and 18˚≤B≤22˚, CLmax was 1.24~1.40. Given the trapezoid kite, CLmax was produced as 1.65~1.89 with A≤1.5 and 34˚≤B≤44˚. And when A=2 and B=14~48, CL was around 1. Given the inverted trapezoid kite, CLmax was 1.57~1.74 with A≤1.5 and 24˚≤B≤36˚. And when A=2, CLmax was 1.21 with B=18˚. 2. For a model with A=1/2, an increase in B caused an increase in CL until CL has reached the maximum. Then there was a tendency of a gradual decrease in the value of CL and in particular, the rectangular kite showed a more rapid decrease. For a model with A=2/3, the tendency of CL was similar to the case of a model with A=1/2 but the tendency was a more rapid decrease than those of the previous models. For a model with A=1, and increase in B caused an increase in CL until CL has reached the maximum. Soon after the tendency of CL decreased dramatically. For a model with A=1.5, the tendency of CL as a function of B was various. For a model with A=2, the tendency of CL as a function of B was almost the same in the rectangular and trapezoid model. There was no considerable change in the models with 20˚≤B≤50˚. 3. The tendency of kite model's CL in accordance with increase of B was increased rapidly than plate models until CL has reached the maximum. Then CL in the kite model was decreased dramatically but in the plate model was decreased gradually. The value of CLmax in the kite model was higher than that of the plate model, and the kite model's attack angel at CLmax was smaller than the plate model's. 4. In the relationship between aspect ratio and lift force, the attack angle wh..
