• International Journal of Naval Architecture and Ocean Engineering
• /
• 제10권4호
• /
• pp.491-498
• /
• 2018

The cost evaluation for voyage route planning in an ice-covered sea is one of the major topics among ship owners. Information of the ice properties, such as ice type, concentration of ice, ice thickness, strength of ice, and speed-power relation under ice conditions are important for determining the optimal route in ice and low operational cost perspective. To determine achievable speed at any designated pack ice condition, a model test of resistance, self-propulsion, and overload test in ice and ice-free water were carried out in a KRISO ice tank and towing tank. The available net thrust for ice and an estimation of the ice resistance under any pack ice condition were also performed by I-RES. The in-house code called 'I-RES', which is an ice resistance estimation tool that applies an empirical formula, was modified for the pack ice module in this study. Careful observations of underwater videos of the ice model test made it possible to understand the physical phenomena of underneath of the hull bottom surface and determine the coverage of buoyancy. The clearing resistance of ice can be calculated by subtracting the buoyance and open water resistance form the pre-sawn ice resistance. The model test results in pack ice were compared with the calculation results to obtain a correlation factor among the pack ice resistance, ice concentration, and ship speed. The resulting correlation factors were applied to the calculation results to determine the pack ice resistance under any pack ice condition. The pack ice resistance under the arbitrary pack ice condition could be estimated because software I-RES could control all the ice properties. The available net thrust in ice, which is the over thrust that overcomes the pack ice resistance, will change the speed of a ship according to the bollard pull test results and thruster characteristics (engine & propulsion combination). The attainable speed at a certain ice concentration of pack ice was determined using the interpolation method. This paper reports a procedure to determine the attainable speed in pack ice and the sample calculation using the Araon vessel was performed to confirm the entire process. A more detailed description of the determination of the attainable speed is described. The attainable speed in 1.0 m, 90% pack ice and 540 kPa strength was 13.3 knots.

• Ocean and Polar Research
• /
• 제36권4호
• /
• pp.487-494
• /
• 2014

Deep-seabed test miner operated by a self-propelled mining system moving on soft soil is an essential device to secure floating and towing performances. The performances of the tracked vehicle are seriously influenced by noise factors such as the shear strength of the seafloor, bottom current, seafloor slope, speed of tracked vehicle, reaction forces of flexible hose, steering ratio, etc. Due to uncertainties related to noise factors, the design of a deep-sea manganese nodules test miner that satisfies target reliabilities is difficult. Therefore, reliability-based design optimization (RBDO) is required to guarantee system reliability under circumstances where uncertainties related to noise factors prevail. Among noise factors, the bottom current, a bimodal distribution, is censored due to the observation limit of measurement devices. Therefore, estimated distribution of the bottom current is inaccurate without considering these characteristics and the result of RBDO cannot be guaranteed. In this paper, we define censored data as unknown values over the limit of observation. If this data is estimated by using Akaike information criterion (AIC) that cannot consider the characteristics of censored data, the distribution of estimated data cannot guarantee accurate reliability. Therefore, censored AIC that can consider the characteristics of data is used to estimate accurate distribution of the bottom current. Finally, RBDO, under circumstances where uncertainties related to noise factors combined censored data are present, is performed on the mobility of a deep-sea manganese nodules test miner.

• 대한조선학회논문집
• /
• 제41권6호
• /
• pp.120-125
• /
• 2004

There are very few numbers of 115K FPP (Fixed Pitch Propulsion) Tankers for the Baltic ice class IA because the minimum power requirement of FMA (Finish- Swedish Maritime Association) needs quite large engine power and the 40 m Beam is out of calculation range of FMA minimum power requirements. The shipyard has no choice except to increase the engine power to satisfy FMA minimum power requirement Rule. And the operation cost, efficiency of hullform and its building cost are not good from the ship owners' point of view To solve this problem, the experience of ice breaking tanker development and the ice tank test results were adopted. The main idea to reduce the ice resistance is by reducing waterline angle at design load waterline. The reason behind the main idea is to reduce the ice-clearing force. Two hull forms were developed to satisfy Baltic Ice class IA. Two ice tank tests and one towing tank test was performed at MARC (Kvaener-Masa Arctic Research Center) and SSMB (Samsung Ship Model Basin) facilities, respectively. The purpose of these tests was to verify the performance in ice and open water respectively The hull form 2 shows less speed loss compared to Hull form 1 in open water operation but hull form 2 shows very good ice clearing ability. finally the Hull Form 2 satisfying Baltic ice class IA. The merit of this hull form is to use the same engine capacity and no major design changes in hull form and other related designs But the hull structure has to be changed according to the ice class grade. The difference in two hull form development methods, ice model test methods and analysis methods of ice model test will be described in this paper.

• 대한조선학회논문집
• /
• 제37권3호
• /
• pp.11-20
• /
• 2000

저속 비대선에서는 추진기면에서의 반류형상이 저항 및 추진성능을 결정하는 중요한 요소가 된다. 그러므로 저속 비대선에서는 선미선형의 형상과 유동현상과의 관계를 파악하는 것이 좋은 선형을 설계하기 위해 필수적이다. 선형 변환을 통해 얻어진 선수부의 모양이 같고 선미부의 모양이 다른 두척의 대형 유조선 선형에 대해 저항 추진 시험과 국부유동 계측 실험을 수행하였다. 이는 우선 선형 변화에 따른 저항 추진 계수의 변화를 정량적으로 제시하고, 이러한 총량적인 계측값과 국부 유동관의 관계를 규명함으로써 선미 선형의 변화에 따른 빌지 보오텍스의 세기의 차이와 이로 인한 저항 및 추진효율의 변화 등을 설명하였다. 또한 계측된 실험 자료는 저속 비대선 주위의 유동에 대한 CFD 계산의 검증 자료로 활용할 수 있으리라 기대된다.

• 한국해양환경ㆍ에너지학회지
• /
• 제2권1호
• /
• pp.40-48
• /
• 1999

해양공학과 관련된 모형실험을 위하여 많이 사용되고 있는 조파수조(2차원수조, 장수조, 사각수조)에 소파장치는 필수적인 장치이다. 본 논문에서는 새로운 개념의 소파장치의 소파성능을 실험을 통하여 살펴보았다. 새로 고안된 소파장치는 소파성능이 우수하고 가볍기 때문에 설치가 용이하다. 또한 넓은 설치공간이 필요치 않아 수조공간 활용에 있어 효과적이며 조파기로부터 발생된 파장에 큰 영향을 받지 않기 때문에 아주 큰 장파만 피한다면 거의 완벽하게 파를 소멸시킬 수 있는 장점을 가지고 있다. 본 소파장치는 일정한 크기의 구멍이 균일하게 배열된 타공판을 입사파의 진행방향과 수평으로 수면밑에 잠기게 설치한 형태로 파가 수평형 타공판을 통과하면서 타공판의 구멍을 통하여 강한 제트 흐름이 형성되면서 파 에너지가 소멸되는 특징을 가지고 있다. 모형실험 결과 수평형 타공판의 소파성능은 타공판의 잠긴 깊이와 판의 전체면적과 뚫린 부분의 면적의 비로 표현되는 공극율에 밀접한 관련이 있으며, 각각의 값은 최대 소파성능을 발휘하는 최적의 값을 가지고 있음을 규명하였다. 수평형 타공판의 앞쪽을 뒤쪽보다 약간 기울게 설치하는 방법도 특정한 주파수 범위내에서는 수평형에 비하여 우수한 소파성능을 보이며, 이때 타공판의 경사각도도 소파장치 성능을 결정하는데 중요한 변수임을 밝혔다.

• 대한조선학회논문집
• /
• 제38권1호
• /
• pp.52-61
• /
• 2001

최근에 선형의 유체성능 평가에 활용되기 시작한 CFD 계산결과의 검증을 위해서는 잘 정리된 선체 주위의 국부유동 계측자료의 확보가 필수적이다. 그동안 국내에서 저항성능 평가를 위한 검증자료의 확보를 위해 모형선이 직진하는 경우에 대한 유동 계측이 몇 차례 수행되었다. 본 논문에서는 VLCC 모형의 사항 중 발생하는 여러 개의 분리된 보오텍스 등 매우 복잡한 선미 유동장을 계측함으로써 조종성 계수 추정을 위한 수치계산 결과의 검증 자료를 확보하고자 하였다. 선체가 표류각 $0^{\circ},\;5^{\circ}$와 $10^{\circ}$를 가지고 진행할 때, St. 2와 A.P. 위치에서 좌현 및 우현의 속도장을 각각 계측하였으며, 표류각이 큰 경우에는 각각 발생 위치가 다른 네 개의 보오텍스가 선미에 나타나는 것을 확인할 수 있었다.

• 대한조선학회논문집
• /
• 제49권5호
• /
• pp.367-375
• /
• 2012

In this study, hull form of main vessel of Korean large purse seiner fishing industry is developed for the improvement of resistance performance as well as for the satisfaction to the Standard of Fishing Convention, ILO. Through the modification of reference hull form parameters and local characteristics, the hull form development is carried out. The optimum hull form parameters are searched by Sequential Quadratic Programing(SQP) method with the power estimation method of Holtrop & Mannen. To minimize the wave resistance, bulbous bow parameters are determined by the bulbous bow design method of Alvarino. The plasmatic curve is redesigned from that of the reference hull by using Lackenby method. The resistance performances of the reference and designed hull forms are estimated by using numerical simulation method. Also, the judgment of seakeeping ability and the estimation of intact stability for the designed hull form is carried out. As a result, the optimum hull form is proposed. To verify the improvement of resistance performance, model tests are carried out in towing tank. The results show that the resistance of the designed hull form is about 14% smaller than that of the reference hull from at design speed. A new hull form proposed in this study can contribute to the development of the main vessel hull form of Korean large purse seiner fishing system.

• 대한조선학회논문집
• /
• 제49권5호
• /
• pp.416-424
• /
• 2012

The MAU series has been usually used for the fishing vessel's propeller, which has been improved in consideration of the efficiency as well as the cavitation point of view in Pusan National University. The high efficiency standard series propeller(KF series) has been applied to the design of 52ton class fishing vessel's propeller in the previous study. The experimental study for the performance of the design propellers called KF series for 52 ton class fishing vessel has been conducted with five cases in Korea Ocean Research & Development Institute towing tank. The model tests have been carried out at different pitch ratio and expanded area ratio in comparison with the standard propeller to make the series chart. The KF series chart and the formula for performance expression have been completed on the basis of the experiment result.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제7권1호
• /
• pp.100-114
• /
• 2015

This paper deploys optimization techniques to obtain the optimum hull form of KSUEZMAX at the conditions of full-load draft and design speed. The processes have been carried out using a RaPID-HOP program. The bow and the stern hull-forms are optimized separately without altering neither, and the resulting versions of the two are then combined. Objective functions are the minimum values of wave-making and viscous pressure resistance coefficients for the bow and stern. Parametric modification functions for the bow hull-form variation are SAC shape, section shape (U-V type, DLWL type), bulb shape (bulb height and size); and those for the stern are SAC and section shape (U-V type, DLWL type). WAVIS version 1.3 code is used for the potential and the viscous-flow solver. Prior to the optimization, a parametric study has been conducted to observe the effects of design parameters on the objective functions. SQP has been applied for the optimization algorithm. The model tests have been conducted at a towing tank to evaluate the resistance performance of the optimized hull-form. It has been noted that the optimized hull-form brings 2.4% and 6.8% reduction in total and residual resistance coefficients compared to those of the original hull-form. The propulsive efficiency increases by 2.0% and the delivered power is reduced 3.7%, whereas the propeller rotating speed increases slightly by 0.41 rpm.

• 해양환경안전학회지
• /
• 제20권4호
• /
• pp.405-411
• /
• 2014

사고선박의 2차적인 피해를 줄이기 위해서는 사고선박을 안전한 곳으로 이동시키기 위한 예인선의 소요마력 산출이 요구되며, 길이 93 m 여객선형 대상선박에 대한 실선실험을 통하여 소요마력 산출에 대한 이론적인 계산식의 유효성을 검증하였다. 실선실험 결과는 이론계산 결과와 비교해 볼 때 상당히 일치되어 예선의 소요마력 산정을 위해 사용하기에 충분하다고 판단되며, 정적저항에서 공기저항, 마찰저항, 잉여저항과 더불어 프로펠러 고착저항이 상대적으로 큰 값으로 평가되었다. 피예인선은 예인과정에서 좌우 측면으로 $30^{\circ}$정도까지 스윙운동 및 요우잉이 발생하였으며, 이로 인한 동적저항이 큰 값으로 평가되었다. 추후 안전율에 대한 연구가 필요할 것으로 판단되며, 저항의 정확한 예측을 통하여 안전율을 최소화함으로써 경제적인 예인선의 사용이 가능할 것으로 판단된다.