• 한국해양공학회지
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• 제37권5호
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• pp.181-189
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• 2023

The fuel consumption of marine diesel engines holds paramount importance in contemporary maritime transportation and shapes energy efficiency strategies of ocean-going vessels. Nonetheless, a noticeable gap in knowledge prevails concerning the influence of ship hull conditions and propeller roughness on fuel consumption. This study bridges this gap by utilizing artificial intelligence techniques in Matlab, particularly convolutional neural networks (CNNs) to comprehensively investigate these factors. We propose a time-series prediction model that was built on numerical simulations and aimed at forecasting ship hull and propeller conditions. The model's accuracy was validated through a meticulous comparison of predictions with actual ship-hull and propeller conditions. Furthermore, we executed a comparative analysis juxtaposing predictive outcomes with navigational environmental factors encompassing wind speed, wave height, and ship loading conditions by the fuzzy clustering method. This research's significance lies in its pivotal role as a foundation for fostering a more intricate understanding of energy consumption within the realm of maritime transport.

• 대한조선학회논문집
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• 제47권3호
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• pp.377-387
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• 2010

In this study, the turbulent free surface around KVLCC1 employed in the circular motion test simulation is numerically calculated using a commercial CFD(Computational Fluid Dynamics) code, FLUENT. Also, hydrodynamic forces and yaw moments around a ship model are calculated during the steady turning. Numerical simulations of the turbulent flows with free surface around KVLCC1 have been carried out by use of RANS equation based on calculation of hydrodynamic forces and yaw moments exerted upon the ship hull. Wave elevation is simulated by using the VOF method. VOF method is known as one of the most effective numerical techniques handling two-fluid domains of different density simultaneously. Boundary layer thickness and wake field are changed various yaw velocities of ship model during the steady turning. The calculated hydrodynamic forces are compared with those obtained by model tests.

• 한국항해학회지
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• 제17권1호
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• pp.37-48
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• 1993

When the vessel is running at the very low Froude numbers, the free-surface is difficult to be disturbed, wave-making is negligible, and the double -model velocity potential gives a very good approximation for calculating the velocity distribution just outside the boundary layer. If the speed of incident flow is gradually increased, the most perceptible change is the rise of the flow surface at stem. With further increase in speed, the nature of the flow at the bow changes completely, The flow ahead of the bow becomes more distrubed, the rise at the stem to stagnation height disappear, and the first wave crest, of less than the stagnation height, appears a small distance downstream from the stem. The present study is concerned with a small region of this flow, mainly in the bow region. The present investigation is primarily an experimental study of the flow in the bow region of s ship model, and it is undertaken in order to investigated systematically, the effect of bow geometry on this flow. The long-range objective is to use these results to guide the development of a mathematical model for predicting the flow about a ship's bow.

• 한국군사과학기술학회지
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• 제20권2호
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• pp.197-205
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• 2017

During the sea trial, we discovered EMI between MOSCOS and ES DF antenna. CW emitted by MOSCOS raised the threshold level of ES DF antenna. As a result, direction finding rate of ES has been decreased. This is a study for the improvement of EMI between the antennas mounted on a surface ship. An analysis is accomplished for MOSCOS, ES DF antenna and Jamming transmitter. This paper presents the method how to solve EMI based on the measurements and calculations about the ES DF antenna receiving level, MOSCOS radiation pattern and Jamming transmitter thermal noise. The test was performed with optimal deployment of MOSCOS on a surface ship. After changing the position of MOSCOS, EMI has been decreased significantly.

• 대한조선학회논문집
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• 제53권1호
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• pp.45-53
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• 2016

The interaction between the hull of ship and free surface of water generates important loads during slamming motion. In the present study, the slamming load applied on the sectional surface of two-dimensional arbitrary bodies has been investigated under several falling velocities. This simulation has been done with the commercial CFD software ANSYS FLUENT^®. Through the conventional MARINTEK experiments for the benchmark of the simulation, we verified the impact pressure values between the experiments and simulation results. Two arbitrary ship bow section models, Panamax-like(with small convex bulb and flare) and Post panamax-like(with large convex bulb and flare) are also investigated. Simulation results show that a maximum impact pressure on the Post panama-like shape is higher than the Panamax-like shape. According to both a lump of water generated by arbitrary shape and various dead-rise angles of the shape, the pressure picks were enhanced in the simulation.

• Ocean Systems Engineering
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• 제1권1호
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• pp.17-28
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• 2011

The purpose of this paper is to demonstrate the efficacy of modeling a surface effect ship's air-cushion flexible seal utilizing a two-dimensional beam under steady state conditions. This effort is the initial phase of developing a more complex three-dimensional model of the air-seal-water fluid-structure interaction. The beam model incorporates the seal flexural rigidity and mass with large deformations while assuming linear elastic material response. The hydrodynamic pressure is derived utilizing the OpenFOAM computational fluid dynamic (CFD) solver for a given set of steady-state flow condition. The pressure distribution derived by the CFD solver is compared with the pressure required to deform the seal beam model. The air pressure, flow conditions and seal geometry are obtained from experimental analysis. The experimental data was derived from large-scale experimental tests utilizing a test apparatus of a canonical surface effect ship's flexible seal in a towing tank over a variety of test conditions.

• 대한조선학회논문집
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• 제33권1호
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• pp.19-26
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• 1996

프로펠러에 의한 선체변동압력을 추정하기 위해 3개의 선체에 7개의 프로펠러를 장착하여 실험과 계산치를 비교하였다. 변동압력의 계측은 KRISO의 공동터널에서 평판에 대하여 수행하였으며, 수치계산은 양력면 이론과 패널법을 사용한 수치프로그램(X-ForShip)을 사용하였다. 평판에 대한 실험값을 복잡한 선미형상에 적용하기 위하여 강체경계율(SBF)이 수정계수로 결정되었다. 실선 변동압력의 예측과 실험치의 수정을 위하여 복잡한 선미형상에서의 변동 압력을 계산하였다. 계산치와 수정된 실험치와의 좋은 일치를 보였으며, 수성계수로써 약 0.65-0.7의 값이 결정되었다.

• 한국군사과학기술학회지
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• 제12권1호
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• pp.8-17
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• 2009

This paper proposes robust ship wake search method in the target evasion environment. Moving surface ships generate a long trailing wake in the rear of a surface ship. Wake homing torpedo sensing this wake can detect the surface target and engage it automatically. In wake homing torpedo, wake search method is important element to maximize effectiveness of wake homing torpedo. This paper proposes one-side, two-side and centering mode according to passing wake boundary scenarios. Also, wake deflection angle is deduced by using the principle of deflection angle of acoustic torpedo. The representative experimental results using monte-carlo simulation demonstrate that the searching method using one-side mode is superior to two-side and centering mode in the target evasion environment.

• Strategy21
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• 통권44호
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• pp.377-416
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• 2018

The purpose of this study is to investigate the effects of the job stresses perceived by R.O.K. naval crews on turnover intentions and job satisfactions. Especially, this study aims to derive the policy implication for the trait characteristics by comparing the job attitude between the surface naval ship and submarine crew. For this purpose, we surveyed 1,000 naval crews. Then, multiple regression analysis was performed. Next, a T-test was conducted to test statistical significance of group differences. First, the job stresses perceived by naval crews were higher in the order of physical environments, overworks, compensation incompetence, lacks of autonomy, and conflicts with people. Second, the job stresses perceived by submarine crews were higher than that of surface naval ship crews. It was also proved statistically significant by the T-test. Third, the physical environments, lacks of autonomy, conflicts of relativity, and inadequate compensation stress have a positive statistically significant effect on turnover intentions of naval crews. Fourth, lacks of autonomy, conflicts of relativity, and inadequate compensation factors have a statistically significant negative effect on the job satisfactions of naval crews. Finally, multiple regression analysis was performed between the independent and dependent variables of the naval crews, and the policy implications were derived.

• 대한조선학회논문집
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• 제31권2호
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• pp.15-21
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• 1994

전산기를 이용한 순정작업은 크게 두 가지로 구분할 수 있다. 첫번째는 단면곡선, 즉 2차원 곡선을 순정하고 다른 단면에서도 역시 부드러운가를 확인하는 전통적인 방법이다. 두번째는 곡면을 이용하는 것으로 전산기의 발달과 더불어 최근 많이 사용하고 있는 방법이다. 그러나 이 경우 먼저 선형을 곡면으로 정의하여야 하나 복잡한 선형의 경우 쉽지가 않다. 본 연구에서는 곡선의 순정기법을 확장하여 그물망 곡선(mesh curve)의 경우에 대해 비균일(non-uniform) B-Sp line 곡선을 이용한 Rong의 방법으로 선형의 순정작업을 행하였다. 그러나 Rong의 방법에는 곡선의 양 끝점에서의 기울기가 고정되어야 하는 제한이 있으며 곡면화 방법에 대한 기술이 명확하지 못하다. 본 연구에서는 곡선의 양끝의 기울기를 고정시키지 않고 순정작업을 할 수 있도록 하였으며, 순정된 결과를 곡면화하는 방법을 제안하였다.