• 한국해양공학회지
• /
• 제31권5호
• /
• pp.335-339
• /
• 2017

This study investigated the sea trial performance of a wave piercing high speed planing hull (WPH). The bow shape of the boat is sharp, and it has no chine or spray strip like a normal planing boat. The skeg is attached to the bottom of the boat in the longitudinal direction from the bow to the stern. The speed performance was analyzed as the speed dropped in a wave, and the seakeeping performance was compared with that of a planing boat with a similar velocity coefficient by measuring the vertical acceleration of the bow in the wave. The turning circle was compared with Lewandowski's estimation for a planing boat. As a result of this study, it was confirmed that the velocity drop of the developed WPH was not large in a wave, and the vertical acceleration was greatly reduced compared with that of a normal planing boat. The turning circle was somewhat larger than the estimated results for a planing boat, but the overall tendency was the same.

• 한국항해항만학회:학술대회논문집
• /
• 한국항해항만학회 2005년도 춘계학술대회 논문집
• /
• pp.41-46
• /
• 2005

본 연구에서는 자유수면 위를 고속으로 항주하는 트랜섬 선미를 채택한 선박에 의하여 발생되는 선박주위 및 트랜섬 선미 끝단에서의 비선형 자유수면 경계조건을 만족하는 자유수면에서의 유동 및 파형을 해석하는 수치해석기법에 대하여 연구하고 포텐셜 유동해석기법인 랜킨소오스 패널법을 사용하여 선체주위 유동해석 프로그램을 개발하였다. 개발된 수치해석 프로그램의 타당성을 검증하기 위하여 고속선인 Athena선형, KCS(KRISO container ship)선형에 대하여 수치해석을 수행하였으며, 그 결과를 모형시험에 의하여 계측된 실험결과와 서로 비교하였다.

• 대한조선학회논문집
• /
• 제46권6호
• /
• pp.587-594
• /
• 2009

In the paper the effect of a stern-plate attached to a ship was taken into account. The relationship between the trim angle of a ship and the wave-resistance coefficient induced by the a stern-plate was studied using the potential flow analysis method. Numerical algorithm was described using the panel method and the vortex lattice method(VLM) to simulate the flow phenomena around a ship. The non-linearity of the free surface boundary conditions were considered using the iterative method and the IGE-GMRES(Incomplete Gaussian Elimination-The Generalized Minimal RESidual) algorithm was adopted to solve the linear equation at each iterative step. Numerical calculations were carried out to investigate the validity of the adopted algorithm using KCS(KRISO 3600 TEU Container) hull. Possible cases for attachment of the plate were checked. The results showed that the numerical algorithm could be physically appropriate.

• 대한조선학회논문집
• /
• 제45권5호
• /
• pp.502-512
• /
• 2008

CFD tools were intensively used to develop a bulk carrier hull form of 180,000 DWT. HCAD and WAVIS were utilized to vary and evaluate the hull forms. LCB and framelines were systematically changed starting from a mothership. Resistance characteristics have been assessed by evaluating the wave-pattern resistance and viscous pressure drag along with the wave profile and wake distribution. It was found that the hull forms obtained from LCB variations were not good enough to satisfy the target resistance coefficient because of large wave generation at the design speed. After choosing the appropriate one from the LCB variation series, bow and stern framelines have been modified to improve wave-making characteristics and wake distribution, respectively. Model tests were performed to confirm the CFD results. Furthermore, the effect of free surface on CFD application was investigated, and a few comments are given on the difference between WAVIS version 1.4 and 2.0.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제13권1호
• /
• pp.65-74
• /
• 2021

A key factor that governs the wave interferences of a submerged body is the dimensionless Froude number. Computational Fluid Dynamics (CFD) is used to describe the resistance force coefficients and the generated waves of two SUBOFF submarine models. Grid independence studies are performed on two cases, totally and shallowly submerged cases, with four sets of computing meshes. The highest peaks are marked by red points at given wavelengths, a line is fitted to those points with a least-squares approximation, and the half wake angle at multiple Froude numbers is defined between the fitted line and the centerline of the free surface. The results show that when the depth of the target is 1.1D, constructive interferences occur at Fn = 0.3 and 0.5, while destructive interference occurs at Fn = 0.35 with distortion of the waveform. The half wake angle is less than 19.47° because of the interference between the bow and stern wave systems.

• 대한토목학회논문집
• /
• 제31권6A호
• /
• pp.425-433
• /
• 2011

본 연구에서는 파랑하중에 의해 부유구조체 하면에서 발생하는 파압 현상을 규명하기 위한 실험적 연구를 수행하였다. 서로 다른 측면 형상과 하면 형상을 갖는 4개의 폰툰형 시험체를 제작하여 5 종류 파랑하중에 대한 수리모형실험을 실시하였다. 시험체의 하면에는 6개의 파압센서를 설치하였으며, 수리모형실험 동안 시험체 하면에 작용하는 파압을 측정하였다. 측정된 파압을 분석한 결과, 와플형의 하면 형상은 부유구조체 하면에 작용하는 파압에 거의 영향을 미치지 않으며, 하이브리드형의 측면 형상은 파압에 상당한 영향을 미치는 것으로 나타났다. 이것은 하이브리드형의 측면에 형성된 에어갭(Airgap)이 부유구조체에 작용하는 파랑의 충격 에너지를 일부 흡수하여 파압을 저감시키는데 기여하는 것으로 판단된다. 기존의 상자형 폰툰과 비교하였을 때 하이브리드형의 파압은 선수부에서 약 83%, 중간부에서 약 74% 및 선미부에서 약 53% 수준인 것으로 나타났다.

• 대한조선학회논문집
• /
• 제37권3호
• /
• pp.1-10
• /
• 2000

저항 및 자항등의 유체성능이 뛰어난 선형을 개발하기 위해서는 선체에 작용하는 여러 방향의 힘은 물론 그러한 결과를 발생시키는 선체 주위의 유동 현상에 대한 이해가 필수적이다. 이러한 국부 유동 현상의 규명을 위해 일반 상선 및 특수선 주위의 전체 파형과 속도 분포 등의 국부 유동현상을 관측할 수 있는 종합적인 국부유동 계측 시스템이 개발되었다. 이를 사용하여 KRISO 3600TEU 컨테이너선(KCS) 주위의 국부유동을 계측하였다. 본 자료는 날씬하고 빠른 현대적인 상선의 유동을 이해하는데 매우 귀중한 자료일 뿐만 아니라 계산유체역학 기법을 이용한 계산 결과의 검증을 위해서도 매우 중요한 자료로 평가된다.

• Journal of Advanced Research in Ocean Engineering
• /
• 제3권2호
• /
• pp.83-101
• /
• 2017

In this study, the added resistances of the large container ship in head and oblique seas are evaluated using a time-domain Rankine panel method. The mean forces and moments are computed by the near-field method, namely, the integration of the second-order pressure directly on the ship surface. Furthermore, a weakly nonlinear approach in which the nonlinear restoring and Froude-Krylov forces on the exact wetted surface of a ship are included in order to examine the effects of amplitudes of waves on ship motions and added resistances. The computation results for various advance speeds and heading angles are validated by comparing with the experimental data, and the validation shows reasonable consistency. Nevertheless, there exist discrepancies between the numerical and experimental results, especially for a shorter wave length, a higher advance speed, and stern quartering seas. Therefore, the accuracies of the linear and weakly nonlinear methods in the evaluation of the mean drift forces and moments are also discussed considering the characteristics of the hull such as the small incline angle of the non-wall-sided stern and the fine geometry around the high-nose bulbous bow.

• 한국해양공학회지
• /
• 제24권2호
• /
• pp.10-17
• /
• 2010

Conventionally, because it is difficult to control a ship in shallow water and because attempting to do so creates unwanted environmental effects, maneuvering ships in the harbor area for berthing is usually done with the assistance of tugboats. In this paper, we propose a new method for berthing ships automatically by using bow and stern thrusters. Specifically, a steering motion model of a ship is considered, and parameters in the equation are evaluated by the system identification technique. An optimal controller based on observations was designed from the linearization of the non-linear ship motion in the horizontal plane. It is used to reduce the uncertainty about the ship's dynamics and reduce measurement requirements. The performance of the controller was also analyzed for its robustness relative to avoiding disturbing the environment due to winds, currents, and wave-drift forces. Experiments were conducted to estimate the potential for identifying result and the design of the controller. Specifically, in this paper, the system modeling and tracking control approach are discussed based on a two-degree-of-freedom (2DOF) servo-system design.

• 해양환경안전학회:학술대회논문집
• /
• 해양환경안전학회 2017년도 공동학술발표회
• /
• pp.123-123
• /
• 2017