• 대한조선학회논문집
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• 제42권4호
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• pp.307-314
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• 2005

In recent years, many environmentally disastrous oil spill accidents from damaged vessels become worse especially when the early treatment is not prompt enough. To properly handle this type of accidents and prevent further disasters, international organizations establish and impose various rules and regulations. In assessing the damages and providing salvage operations, the propulsive performance of damaged vessels is of great importance, as well as for containing oil spill while the vessels are being towed or self-propelled. Until now, many naval hydrodynamics researches have focused on the propulsive performance in normal operating conditions and only a few studies for damaged vessels are found in literature. In this paper experimental method is used to study the Propulsive performance of a very large crude-oil carrier (VLCC) in .heeled and/or trimmed conditions.

• 대한조선학회논문집
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• 제43권3호
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• pp.275-284
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• 2006

In recent years, many environmentally disastrous maritime accidents resulted from oil or fuel spills from damaged vessels. The situation becomes worse especially when the early counter treatment is not prompt enough. To properly handle this type of accidents and prevent further disasters, the propulsive performance of damaged vessels must be better understood for salvage operations, as well as for containing oil spills while the vessels are being towed or self-propelled. Until now, many hydrodynamic studies have focused on the propulsive performance of undamaged vessels but only a few studies on that of damaged vessels. in this paper, both experimental and computational methods are used to study the propulsive performance of a VLCC in heeled and/or trimmed conditions. For experimental studies, measurement systems should be modified to adapt to the variations of attitude of a damaged vessel. For numerical studies, CFD programs should be also extended to be applied to asymmetrically floating conditions.

• 한국전산유체공학회지
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• 제8권2호
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• pp.24-32
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• 2003

In this work, we propose a new idea of flapping airfoil design for optimal aerodynamic performance from detailed computational investigations of flow physics. Generally, flapping motion which is combined with pitching and plunging motion of airfoil, leads to complex flow features such as leading edge separation and vortex street. As it is well known, the mechanism of thrust generation of flapping airfoil is based on inverse Karman-vortex street. This vortex street induces jet-like flow field at the rear region of trailing edge and then generates thrust. The leading edge separation vortex can also play an important role with its aerodynamic performances. The flapping airfoil introduces an alternative propulsive way instead of the current inefficient propulsive system such as a propeller in the low Reynolds number flow. Thrust coefficient and propulsive efficiency are the two major parameters in the design of flapping airfoil as propulsive system. Through numerous computations, we found the specific physical flow phenomenon which governed the aerodynamic characteristics in flapping airfoil. Based on this physical insight, we could come up with a new kind of airfoil of tadpole-shaped and more enhanced aerodynamic performance.

• 한국전산유체공학회지
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• 제20권2호
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• pp.1-6
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• 2015

In this study, a numerical prediction on propulsive performance of a ducted propeller in open water condition was carried out by solving Reynolds averaged Navier-Stokes(RANS) equation using computational fluid dynamics(CFD). A configuration of propeller Ka-470 inside duct 19A was considered. Hexahedral grid system was generated by dividing whole computational domain into three separate regions; propeller, duct and outer flow region. A commercial CFD software, ANSYS-CFX was used for numerical simulations. Results were compared with experimental data and showed considerable improvement in accuracy, in comparison to those from surface panel method which is based on potential flow assumption. The results also exhibited the importance of grid system within the gap between the inner surface of duct and blade tip for accurate prediction of propulsive performance of ducted propeller.

• 한국운동역학회지
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• 제15권3호
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• pp.9-19
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• 2005

The purpose of this study was to analyze the effects of three different types of preparatory movement(squat, countermovement and hopping) in sideward responsive propulsion movement. 7 healthy subjects performed left and right side movement task by external output signal. 3D kinematics were analyzed The results were followed First, performance time in the countermovement and hopping conditions was shorter(10-20%) than that in the squat condition. The hopping condition that is more related to pre-stretch showed excellent performance. Second, time difference between after turned on the external signal and until take off was the primary factor in performance results among movement conditions. The preparatory phase before the propulsive phase in the squat condition produced more time than that in other conditions. The hopping condition showed the most short time in both the preparatory and the propulsive phase, therefore it was advantage for performance result Third, significant difference was not found in take-off velocity among movement conditions although there was difference of the time required in the propulsive phase. The maximum acceleration in the propulsive phase was larger in order of the hopping. countermovement, and squat condition. The countermovement and hopping conditions showed high take-off velocity although the propulsive phase in those conditions was shorter than that in squat condition. The pre-stretch by preparatory countermovement was considered as the positive factor of producing power in concentric contraction. Fourth, the hopping condition produced large angular velocity of joints. In hopping condition, large amount of moment for rotation movement was revealed in relatively short time and it was considered to cause powerful joint movements. In conclusion, the hopping movement using countermovement is advantage of responsive propulsion movement. It is resulted from short duration until take off and large amount of joint moment and joint power in concentric contraction by pre-stretch.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.506-512
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• 2004

We analytically estimated the propulsive performance of pulse detonation engines (PDEs) in three cases, which were (1) a fully-fueled simplified PDE, (2) a partially-fueled simplified PDE, and (3) a PDE optimized as a system. The results of the model analyses in the cases of (1) and (2) were in good agreement with published experimental data which were obtained by using simplified PDEs. The comparison between the results of the analyses of simplified PDEs and those of optimized PDE systems showed that specific impulse would become higher by about 10-20% due to PDE-system optimization.

• 한국기계연구소 소보
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• 통권9호
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• pp.183-191
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• 1982

This report describes the analysis method of the full-scale propulsive performance by using the data of model test and the full-scale speed trial. The model test data were analyzed by the computer program "PPTT" based on "1978 ITTC Performance Prediction Method for Single Screw Ships." Also the full-scale speed trial data were analyzed by the computer program "SSTT" based on the newly proposed “SRS-KIMM Standard Method of Speed Trial Analysis." An analysis of model and full-scale test data was carried out for a 60.000 DWT Bulk Carrier and the correlation between model and full-scale ship was stuied.

• Journal of Ship and Ocean Technology
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• 제8권1호
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• pp.31-41
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• 2004

A ducted marine propulsor has been widely used for the thruster of underwater vehicles for protecting collision damage, increasing propulsive efficiency, and reducing cavitation. Since a single-stage ducted propulsor contains a set of rotor and stator inside an annular duct, the numerical analysis becomes extremely complex and computationally expensive. However, the accurate prediction of viscous flow past a ducted marine propulsor is essential for determining hydrodynamic forces and the propulsive performances. To analyze a ducted propulsor having rotor-stator Interaction, the present work has solved 3D incompressible RANS equations on the sliding multiblocked grid. The flow of a single stage turbine flow was simulated for code validation and time averaged pressure coefficients were compared with experiments. Good agreement was obtained. The hydrodynamic performance coefficients were also computed.

• 대한조선학회지
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• 제27권3호
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• pp.89-99
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• 1990

선박의 운항경제성을 개선하기 위해서는 저항이 작고 추진성능은 우수한 선형의 개발이 요구된다. 흔히, 저저항 특성을 갖는 선미선형은 추진효율이 떨어지는 경우가 많고, 반대로 추진효율이 좋은 선형은 저항이 큰 경우가 많아서 결과적으로 소요마력이 작은 선형의 개발은 어려운 과제로 되어 있다. 비대선형에 있어서는 저항 특히, 점성저항이 작은 것으로 알려진 소위 'Buttock-flow type'의 선미형상을 기본으로 하고, 여기에 추진기 앞쪽(Run부)은 추진효율이 높은 재래 선미형상(U-type 또는 Hogner type)과 같이 만들어 저저항 및 고추진효율의 특성을 함께 갖는 선미선형의 개발을 시도하였다. 최초의 모형시험 결과는 이와같은 시도가 선미선형 설계의 한 접근 방법이 될 수 있음을 보여주었으며, 첫 시험결과에 고무되어 계속적으로 이러한 선미선형의 개량에 주력한 결과로, 저저항 고추진 효율을 갖는 선미선형의 개발에 어느정도 성공을 거두었다. 더하여, 이러한 선형은 추진기 주변의 반류분포가 균일하여 우수한 캐비테이션 및 진동 특성도 함께 가질 수 있고, 종래의 '바-지 선형'에 비하여 기관실 이중저의 상면적(床面積)이 넓어, 보다 경제적인 배치가 가능하다는 것도 확인되었다.

• 대한교통학회:학술대회논문집
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• 대한교통학회 1996년도 제3회 한-중 국제학술회의
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• pp.95-128
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• 1996

Dipped track profiles between rail transit stations can significantly reduce propulsive energy, braking energy and travel times. This work quantifies their potential benefits for circumstances reflected in various values for dips, speed and acceleration limits, station spacings, and available power. A deterministic simulation model has been developed to precisely estimate train motions and performance using basic equations for kinematics, resistance, power and braking. For a dip of 1% of station spacing, in which gradients never exceed 4%, our results show savings (compared with level tracks) exceeding 9% for propulsive energy, 15% for braking energy and 5% for travel time between stations.