• International Journal of Naval Architecture and Ocean Engineering
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• 제3권1호
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• pp.105-110
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• 2011

Some research work on CFD computation of ship motions and added resistance in waves for a high speed trimaran is carried out in this paper. The governing equations, Reynolds Averaged Navier-Stokes and continuity equations are discretized by finite volume method. Volume of fluid method is adopted to deal with the nonlinear free surface. The incident waves are generated from the inflow boundary by prescribing a velocity profile resembling flexible flap wavemaker motions, and the outgoing waves are dissipated inside an artificial damping zone located at the rear part of the wave tank. In this paper, the computed results of ship motion and added resistance for a high speed trimaran are presented. The results of seakeeping experiment for the high speed trimaran carried out in CSSRC towing tank are also presented in this paper. Rather good agreements are shown between the computational and experimental results. The work in this paper provides a numerical tool for the study of seakeeping performance of high speed trimarans.

• 한국항해항만학회지
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• 제38권1호
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• pp.11-18
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• 2014

To confirm whether the square tank at Changwon National University (CWNU) can be used for estimation of maneuverability, planar motion mechanism (PMM) test and circular motion (CM) test were performed for various conditions. PMM test can be implemented using an XY carriage and a yaw table in the square tank. However, sometimes test section is insufficient for PMM test owing to low length-breadth ratio of the tank. In addition, the speed of a towing carriage is also quite limited. Therefore, it would be useful if PMM test could be effectively performed diagonally, by establishing coupled control logic to drive three servomotors. In addition, Froude number dependency on the estimated hydrodynamic coefficients was checked. Furthermore, CM tests, which cannot be completed in a conventional linear towing tank, were performed, and its results were compared with the results of PMM test. The results of the PMM tests in the diagonal direction were consistent with the results of the test performed in the direction parallel to the sidewall. However, the results of the CM test were greater than those of the PMM test. This tendency was also observed in the results published at Ulsan University.

• International Journal of Naval Architecture and Ocean Engineering
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• 제10권5호
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• pp.596-608
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• 2018

The present study aims to assess test uncertainty assessment method of nominal wake field measurement by a Stereoscopic Particle Image Velocimetry (SPIV) system in a towing tank. The systematic uncertainty of the SPIV system was estimated from repeated uniform flow measurements. In the uniform flow measurement case, time interval between image frames and uniform flow speed were varied to examine the effects of particle displacement and flow around the SPIV system on the systematic standard uncertainty. The random standard uncertainty was assessed by repeating nominal wake field measurements and the estimated random standard uncertainty was compared with that of laser Doppler velocimetry. The test uncertainty assessment method was applied to nominal wake measurement tests of a very large crude oil carrier model ship. The nominal wake measurement results were compared with existing experimental database by other measurement methods, with its assessed uncertainty.

• 대한조선학회논문집
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• 제37권3호
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• pp.1-10
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• 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.

• 대한조선학회논문집
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• 제55권2호
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• pp.169-177
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• 2018

Twisted rudder, twisted rudder with bulb, and twisted rudder with bulb and fin have been developed computationally for 3,000 TEU container ship through parametric study. The objective function is to minimize delivered power in model scale. Design variables are twisted angle, rudder bulb diameter and fin angle. The governing equation is Reynolds averaged Navier-Stokes equations in an unsteady turbulent flow and the Reynolds stress model applied for the turbulent closure. A double body model is used for the treatment of free-surface. The calculation was carried out in towing and self-propulsion conditions at design speed. The sliding mesh technique was employed to simulate the flow around the propeller. Form factor is obtained from the towing computation. Self-propulsion point is obtained from the self-propelled computations at two propeller rotating speeds. The delivered power due to the designed twisted rudder, twisted rudder with bulb, and twisted rudder with bulb and fin are reduced by 1.1%, 1.6%, and 2.0%, respectively.

• Journal of Hydrospace Technology
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• 제2권2호
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• pp.68-79
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• 1996

The present report describes the results of the cooperative experimental study organized by the High-Speed Marine Vehicle Committee of the Korea Towing Tank Conference. The study aims to improve model test technique and accuracy and to self-evaluate their own capabilities. The resistance tests of a 23m class planing hull were performed at the towing tanks of the Korea Research Institute of Ships and Ocean Engineering (KRISO), Hyundai Maritime Research Institute (HMRI), Seoul National University (SNU), Inha University (IU) and Pusan National University (PNU). In addition, the longitudinal wave cut was measured antral and analyzed at the KRISO. All the results of total resistance, trim and mean sinkage are presented in this report and the results show fairly good agreements comparing with the ITTC HSMV committee's report.

• 한국해양공학회지
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• 제23권4호
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• pp.38-46
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• 2009

Two sets of numerical simulations were carried out for a planing hull model ship. In the first, the WAVIS 1.4 linear and nonlinear potential solver was utilized with the free support condition, in which the running posture was determined during calculation. The linear and nonlinear potential calculation results showed qualitative agreement in the trim and resistance coefficient with the MOERI towing tank test. However, the nonlinear potential calculation gave better results than the linear method. In the next simulation, Fluent 6.3.26 with a VOF model and the WAVIS 1.4 nonlinear potential solver were used with the given running posture from the measurement carried out in the MOERI towing tank. Fluent with the VOF method had substantially better agreement with model test results than the results from the WAVIS nonlinear potential calculation for the total resistance coefficient, and for the bow and stern wave patterns, in spite of the much greater computational costs. Both methods can be utilized in planing hull design when their limitations are perceived, and the running posture should be predicted correctly.

• 해양환경안전학회지
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• 제18권6호
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• pp.597-603
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• 2012

해상에서의 안전한 예인 업무를 수행하기 위해서는 정확한 예인력의 추정이 필요하며, 이를 위해서는 예선의 저항성능 특성에 대하여 정확히 파악해 두어야 할 필요가 있다. 본 연구에서는 먼저 정수중 예선 주위의 유동 특성 및 예선의 저항추진 성능을 파악하고자 회류수조에서 예선 모형을 이용하여 실험을 실시하였다. 모형실험은 무한수심 조건에서의 1/33.75 축척으로 제작된 예선 모형을 이용하였으며, 설계속도를 7노트로 선정하고 역조와 순조의 조류 영향을 고려하여 5~10노트의 속도 구간에서 각 속도별로 실행하였다. 또한 파랑에 의한 예선의 운동응답 함수와 부가저항을 추정하기 위하여 수치계산을 실행하였으며, 이에 대한 결과를 정수중에서의 실험을 통하여 얻게 된 데이터와 비교하였다. 이와 같은 해석 결과 파랑중 부가저항은 선수파 및 속도가 높아질수록 증가하며, 유효마력은 정수중에 비하여 70 % 정도 증가하고 있는 현상을 확인할 수 있었다.

• 대한조선학회지
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• 제4권1호
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• pp.49-54
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• 1967

The authors considered the effects of trim in the small coastal passenger boat upon resistance in this paper. Any change of trim no matter how small, necessarily produces some effect upon resistance. The relations between the resistance coefficients and trim were investigated through the towing test of the Model $MCI-P_1-65$, Korean Standardized Ship, GT 70 tons passenger boat in the gravitational tank. The Lines of the Model are given in Fig. 1. Principal dimensions and other characteristics vary with the trim in general. Those values varied with the trim for $MCI-P_1-65$ are tabulated in table 1. The resistance was measured at five conditions such as even keel, 0.0273L, (original designed trim) 0.0473L, 0.0663L, 0.0873L trim by the stern, fixing the displacement corresponding to the designed load water line. Model was made of wood in length of 3.5 feet coated with varnish, and without appendages. As the artificial turbulent stimulator, the sand strip method was used. The results of model towing tests, correcting to water temperature of $70^{\circ}F$, were expanded to full scale using the Schoenherr's friction formula and surface roughness allowance coefficient of 0.0004. The authors point out, the following results. 1) Optimum trim which gives the minimum resistance exists for every speed at constant displacement and each comes to the same value. For $MCI-P_1-65$ optimum trim is 0.0673L trim by the stern(Fig.4-The cross curves of the resistancecoefficients). 2) At constant displacement, when LCB(longitudinal position of center of buoyancy) varies with the trim, there exists optimum value of LCB which gives minimum resistance for every speed and each comes to the same value. For $MCI-P_1-65$ optimum position of LCB is 8%L aft from midship section (Fig.6).

• Journal of Advanced Marine Engineering and Technology
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• 제41권4호
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• pp.316-322
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• 2017

본 논문의 주 목적은 수치해석 도구를 활용하여 저항성능 관점에서 우수한 선형을 개발하는 것이다. 최종 개발된 선형의 성능 평가를 위해 수조 모형시험을 수행하였다. 현존선은 도면을 바탕으로 실물과 도면의 타당성 검토를 위해 실태조사를 수행하였다. 실태조사 시에 실제 운항 상태인 주 운항 배수량 및 주 운항 선속을 확인하였다. 수치해석을 바탕으로 현존선의 저항성능을 검토하였다. 개발선은 선수어깨의 파형개선, 배수량 분포의 균형화, 단면형상의 수정 그리고 중앙 스케그의 크기와 형상 변경에 관한 스터디를 통해 도출되었다. 수치해석 결과 개발선은 조파저항 개선에 의해 저항성능 관점에서 주 운항 선속인 11노트에서 약 15% 개선된 양을 보여주었다(Table 4 참조). 개발된 선형의 성능 평가를 위해서 수조 모형시험을 수행하였으며 그 결과 11노트에서 약 17% 개선된 양을 보여주었다(Table 5 참조).