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Kim, Yoo-Chul,Kim, Kwang-Soo,Kim, Jin,Kim, Yoonsik,Park, Il-Ryong,Jang, Young-Hun The Society of Naval Architects of Korea 2017 International Journal of Naval Architecture and Oc Vol.9 No.6
The KVLCC2 and its modified hull form were investigated in regular head waves using Unsteady Reynolds Averaged Navier-Stokes (URANS) methods. The modified KVLCC2 (named KWP-bow KVLCC2) is designed for reducing wave reflection from the bow. Firstly, the original KVLCC2 is studied for verification of the present code and methodology and the computed time history of total resistance and 2DOF motions (heave and pitch) for the selected two wave length conditions are directly compared with the results obtained from KRISO towing tank experiment under the identical condition. The predicted added resistance, heave and pitch motion RAOs show relatively good agreement with the experimental results. Secondly, the comparison of performance in waves between KVLCC2 and KWP-bow KVLCC2 is carried out. We confirmed that newly designed hull form shows better performances in all the range of wave length conditions through both the computation and the experiment. The present URANS method can capture the difference of performance in waves of the two hull forms without any special treatment for short wave length conditions. It can be identified that KWP-bow KVLCC2 gives about 8% of energy saving in sea state 5 condition.
김유철,김광수,김진하,김윤식,박일룡,장영훈 대한조선학회 2017 International Journal of Naval Architecture and Oc Vol.9 No.6
The KVLCC2 and its modified hull form were investigated in regular head waves using Unsteady Reynolds Averaged NaviereStokes (URANS) methods. The modified KVLCC2 (named KWP-bow KVLCC2) is designed for reducing wave reflection from the bow. Firstly, the original KVLCC2 is studied for verification of the present code and methodology and the computed time history of total resistance and 2DOF motions (heave and pitch) for the selected two wave length conditions are directly compared with the results obtained from KRISO towing tank experiment under the identical condition. The predicted added resistance, heave and pitch motion RAOs show relatively good agreement with the experimental results. Secondly, the comparison of performance in waves between KVLCC2 and KWP-bow KVLCC2 is carried out. We confirmed that newly designed hull form shows better performances in all the range of wave length conditions through both the computation and the experiment. The present URANS method can capture the difference of performance in waves of the two hull forms without any special treatment for short wave length conditions. It can be identified that KWP-bow KVLCC2 gives about 8% of energy saving in sea state 5 condition.
Effect of ship motions on added resistance in regular head waves of KVLCC2
Yu, Jin-Won,Lee, Cheol-Min,Choi, Jung-Eun,Lee, Inwon Elsevier 2017 Ocean engineering Vol.146 No.-
<P><B>Abstract</B></P> <P>This paper employs an experimental method to investigate the impact of ship motions on added resistance for KVLCC2 advancing forward in 14 regular head waves. The model tests have been conducted at Pusan National University's towing tank. The model is free or fixed to surge. The wave length ranges from 0.3LPP to 1.9LPP. In the case of λ = 0.6LPP, three more wave steepnesses and surge-fixed conditions have been taken into consideration. The wave elevation, surge, sinkage, trim and resistance have been measured. The measured data are filtered using moving-average-filter method. The filtered data have been analyzed by using the Fourier series. The mean values and phases of the total resistance in waves are nearly the same as at the surge-free and -fixed conditions. The magnitude of the added resistance is influenced by that of the bow relative motion. The phase of the added resistance shows similar trends to those of the surge and bow relative motions. The non-linearity of the added resistance increases in tandem with the wave steepness, although the RAOs of ship motions show linearity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> This paper presents the characteristics of the ship motions and the added resistance in regular head waves for the KVLCC2. </LI> <LI> The influence of surge-fixed and -free conditions on the total resistance in waves is described. </LI> <LI> The relationship between the added resistance in waves and the ship motion characteristics is discussed. </LI> <LI> In short length, three more wave heights have been conducted to know the wave steepness effect. </LI> </UL> </P>
Numerical Analysis of Added Resistance and Vertical Ship Motions in Waves for KVLCC2
Mingyu Kim,Dong-Woo Park 해양환경안전학회 2016 해양환경안전학회지 Vol.22 No.5
본 연구에서는 KVLCC2의 파랑 중 부가저항과 운동을 Unsteady Reynolds-Averaged Navier-Stokes(URANS) 방법과 3차원 포텐셜법을 이용하여 추정하였다. 수치해석은 3가지 선박속도(설계, 운항, 정지 속도)에서 다양한 파랑조건에서의 선박의 부가저항 및 수직운동(상하 및 종 동요 응답)의 추정에 대해 수행되었다. 첫째, CFD와 3차원 포텐셜 방법을 이용하여 규칙파에서의 선박속도와 파랑조건에 따른 선박의 부가저항과 운동을 추정하고 실험값과의 비교를 통해 두 수치 해석법의 특징을 살펴보았다. 둘째, CFD를 이용한 선박의 속도별 비정상 파형 분포와 선박의 부가저항 및 운동의 시간이력에 대해 해석하였다. 수치 격자계에 대한 수렴도를 확인하였고 수치계산과 모형시험 결과를 비교하여 사용한 수치 기법들을 체계적으로 검증 하였다. 이를 통해 본 연구에 적용된 수치해석법들의 신뢰성과 선속변화에 따른 파랑 중 부가저항과 선박의 수직운동에 대한 관계를 확인하였다. The present study provides numerical simulations to predict the added resistance and ship motion of the KVLCC2 in regular waves using the unsteady Reynolds-Averaged Navier-Stokes (URANS) and 3-D potential methods. This numerical analysis is focused on added resistance and vertical ship motions (heave and pitch) under a wide range of wave conditions at three ship speeds (design, operating and zero speeds). Firstly, the characteristics of the CFD and 3-D potential flow methods are presented to predict added resistance and ship motions in regular waves taking into account various wave conditions at design speed to provide a validation study as well as at operating and zero speeds. Secondly, analyses of added resistance and ship motion with unsteady wave patterns and time history results as simulated by CFD were performed at each ship speed. Systematic validation and verifications of the numerical computations in this study were made against available Experimental Fluid Dynamics (EFD) data including grid convergence tests to demonstrate that reliable numerical results were obtained for the prediction of added resistance and ship motion in waves. Relationships between added resistance, vertical motion and changes in ship speeds were also found.
Reduction of UKC for Very Large Tanker and Container Ship in Shallow Water
Lee, Sang-Min The Korean Society of Marine Environment and safet 2021 海洋環境安全學會誌 Vol.27 No.3
The decrease in under keel clearance (UKC) due to the increase of draft that occurs during advancing and turning of very large vessels of different types was analyzed based on computational fluid dynamics (CFD). The trim change in the Duisburg test case (DTC) container ship was much smaller than that of the KRISO very large crude oil carrier 2 (KVLCC2). The sinkage of both ships increased gradually as the water depth became shallower. The amount of sinkage change in DTC was greater than that in KVLCC2. The maximum heel angle was much larger for DTC than for KVLCC2. Both ships showed outward heel angles up to medium-deep water. However, when the water depth became shallow, an inward heel was generated by the shallow water effect. The inward heel increased rapidly in very shallow water. For DTC, the reduction ratio was very large at very shallow water. DTC appeared to be larger than KVLCC2 in terms of the decreased UKC because of shallow water in advancing and turning. In this study, a new result was derived showing that a ship turning in a steady state due to the influence of shallow water can incline inward, which is the turning direction.
Cheol-Min Lee,Jin-Hyeok Seo,Jin-Won Yu,Jung-Eun Choi,이인원 대한조선학회 2019 International Journal of Naval Architecture and Oc Vol.11 No.2
This paper employs computational tools to predict power increase (or speed loss) and propulsion performances in waves of KVLCC2. Two-phase unsteady Reynolds averaged Navier-Stokes equations have been solved using finite volume method; and a realizable k-ε model has been applied for the turbulent closure. The free-surface is obtained by solving a VOF equation. Sliding mesh method is applied to simulate the flow around an operating propeller. Towing and self-propulsion computations in calm water are carried out to obtain the towing force, propeller rotating speed, thrust and torque at the selfpropulsion point. Towing computations in waves are performed to obtain the added resistance. The regular short head waves of l/LPP ¼ 0.6 with 4 wave steepness of H/l ¼ 0.007, 0.017, 0.023 and 0.033 are taken into account. Four methods to predict speed-power relationship in waves are discussed; Taylor expansion, direct powering, load variation, resistance and thrust identity methods. In the load variation method, the revised ITTC-78 method based on the ‘thrust identity’ is utilized to predict propulsive performances in full scale. The propulsion performances in waves including propeller rotating speed, thrust, torque, thrust deduction and wake fraction, propeller advance coefficient, hull, propeller open water, relative rotative and propulsive efficiencies, and delivered power are investigated.