• 대한조선학회논문집
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• 제44권3호
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• pp.258-266
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• 2007

CFD calculations are performed for KRISO 3600TEU container ship(KCS) models with different Reynolds numbers. Numerical calculations of the turbulent flows with the free surface around KCS have been carried out at $Re=0.791{\times}106\;and\;Re=1.4{\times}107$ using a standard Fluent package. In both cases, Froude number is fixed with 0.26 and wave elevation is simulated by using the VOF method. The calculated results at $Re=1.4{\times}107\;and\;Re=0.791{\times}106$ are compared with the experiment data of KRISO towing tank test and RIMS CWC test, respectively. Boundary layer thickness and wake field shows Reynolds number differences. There are some changes in wave pattern behind transom stern.

• 해양환경안전학회지
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• 제27권7호
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• pp.1106-1115
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• 2021

본 연구에서는 80k Bulk carrier의 저항성능 향상을 목적으로 선미부에 1개의 핀을 부착해 선미 유동을 제어하였고, 저항성능 및 반류의 변화를 분석하였다. 부착된 핀은 직사각형 단면을 가지며, 길이와 폭, 두께는 고정된 채 길이 및 흘수 방향 부착 위치와 유선에 대한 각도만 변화가 있었다. 나선 및 핀이 부착된 선체에 대한 모형 스케일에서의 CFD 해석이 수행되었고, 그 결과를 실선 확장 후 비교하였다. 핀은 프로펠러로 유입되는 빌지 볼텍스의 경로를 선미 트랜섬 쪽으로 변화시켰고, 이는 프로펠러 상부와 선미부의 압력을 증가시켰다. 이로 인해 선체의 압력저항 및 전 저항이 감소되었으며, 감소율은 핀의 부착 위치가 선미 및 선저와 가까울수록 높았다. 또한 핀은 공칭반류를 감소시켰는데 핀의 각도가 커질수록 반류의 변화가 컸고, 전 저항 저감률은 최대가 되는 특정 각도까지만 비례하였다. 대상 선박에 단일 핀을 부착했을 시의 최대 전 저항 저감률은 약 2.1 %였고, 선미로부터 수선간장의 12.5%, 선저로부터 흘수의 10 % 위치에 14°의 각도로 부착됐을 때이다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.381-384
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• 2002

The free surface flow problem has been one of the most interesting and challenging topic in the area of the naval ship hydrodynamics and ocean engineering field. The problem has been treated mainly in the scope of the potential theory and its governing equation is well known Laplace equation. But in general, the exact solution to the problem is very difficult to obtain because of the nonlinearlity of the free surface boundary condition. Thus the linearized free surface problem has been treated often in the past. But as the computational power increases, there is a growing trend to solve the fully nonlinear free surface problem numerically. In the present study, a time-dependent finite element method is developed to solve the problem. The initial-boundary problem is formulated and replaced by an equivalent variational formulation. Specifically, the computations are made for a highly nonlinear flow phenomena behind a transom stern ship and a vertical strut piercing the free surface.

• 대한조선학회지
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• 제9권1호
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• pp.1-6
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• 1972

To contribute towards more accurate estimation of the virtual coefficient for the vertical vibration of the chine-type ship, experimentally obtained three-dimensional correction factors, J, of added mass of prismatic beams having cross section shape of hypotrocoid characters, slightly concaved Lewis form and elliptic form are investigated in connection with the applicability of an approximate analytical calculation method compared to that proposed by T. Kumai[6] for the Lewis form cylinders, and synthetically in compared with the experimental works on various cross section shapes of the other type by L.C. Burril et al[8] and the analytical works on the ellipsoid of revolution by F.M. Lewis[1] and J.L. Taylor[2]. The experimental results show that the aforementioned analytical method gives, unlike that for the Lewis form cylinders, considerably larger J-values for the chine-type cylinders, and that the influence of the character of the cross section shape on J-values is not remarkable in practical sense. Finally, considering in synthesis the experimental results on prismatic beams, the Burril's works on palabolic plan form and elliptic plan form, and that the chine-type ship usually has a hull form of transom stern, it is fairly safe to say, at the present stage, that adoptation of the Taylor's J-values will not results in any large error in estimation of the virtual inertia coefficients of the chine-type ships.

• 대한조선학회논문집
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• 제31권3호
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• pp.31-37
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• 1994

선체 형상을 표현하기 위하여 Bi-Cubic B-spline이 가장 널리 사용되고 있다. B-spline곡선 곡면 정의에 있어서 입력 데이터가 불규칙하거나, 주어진 데이터의 갯수가 많은 경우, 또는 형상이 복잡한 경우에 주어진 형상의 부드러운 곡선 곡면(Smooth curves or surfaces)을 재현할 수 있는 역행렬을 구하기 어렵다. 이러한 문제점을 극복하기 위해 새로운 버텍스 산출법(ISE 방법: Image Surface Expansion Method)을 제시한다. 곡선정의를 이용하여 ISE방법을 검증하였고, 수렴성을 확인하였다. 또한 선체형상을 정의하였으며, Open Uniform B-spline으로 형성된 곡면과 비교하였고, ISE방법의 신뢰도를 검증하였다.

• 한국해양환경ㆍ에너지학회지
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• 제9권2호
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• pp.92-97
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• 2006

수치계산을 통해 소형 고속선의 선형설계를 수행하였다. 선형변환 프로그램인 HCAD를 사용하고 차인형 선형을 기준선으로 하여 둥근바닥 선형을 설계하였다. WAVIS를 시용하여 두 가지 선형에 대한 선체주위의 유동장과 조파저항 계산 결과를 보였다. 차인형 선형의 저항특성이 둥근 바닥선형에 비해 다소 크게 나타났으나 소형 조선소의 건조비를 감안하여 차인형 선형의 선수부 개량과 선미 웨지의 설계를 통해 조파저항의 감소를 시도하였다. 수치계산 결과 선미 웨지의 적용에 의해 차인형 선형의 조파저항성능이 고속영역에서 개선되었음을 확인하였다.

• 대한조선학회논문집
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• 제43권1호
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• pp.134-146
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• 2006

This paper presents the primary conceptual design results of twenty-passenger class Wing-In-Ground(WIG) effect craft. As a first step, top level requirements were proposed and principal dimensions were determined. Maximum speed in ground effect condition is 150 km/h with two tons payload including passengers. Total weight is estimated as 8.5 tons with 2 tons of thrust. Hull and airfoil sections were designed and self propulsion tests were performed by radio controlled model. Two planing hull forms with the transom stern were proposed and towing tests were performed. The resistance and running attitude were measured and the feasibility is checked for the prototype hull form of the twenty-passenger class WIG craft. The free running tests show the stable smooth running attitude at designed speed. Also this radio controlled model can take off around 0.15 meter wave height. It can be said that the top level requirement for the twenty passenger class WIG ship is satisfied successfully. The design optimization to increase the transport efficiency and safety will be performed in the near future.