• Journal of the Society of Naval Architects of Korea
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• v.51 no.5
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• pp.396-408
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• 2014

In this study, uncertainty analysis based on ITTC(International Towing Tank Conference) Recommended Procedures is carried out in the towing-tank experiment for motion responses and added resistance. The experiment was conducted for KVLCC2 model in head sea condition. The heave, pitch and added resistance were measured in different wave conditions, and the measurement was repeated up to maximum 15 times in each wave condition in order to observe the uncertainty of measured data. The uncertainty analysis was carried out by adopting the ISO-GUM(International Organization for Standardization, Guide to the Expression of Uncertainty in Measurements) method recommended by ITTC. This paper describes the details about the analysis method, uncertainty and the measured uncertainty for each source. The uncertainty analysis results are summarized as a tabular form. To validate the accuracy of the present measurement, the experimental results are compared with the results of numerical computation and other experiment. From the present uncertainty analysis, the main sources of uncertainty are identified, which can be very useful to improve the accuracy for added resistance experiment.

• Journal of the Society of Naval Architects of Korea
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• v.54 no.2
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• pp.132-142
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• 2017

As the International Maritime Organization (IMO) recently introduced the Energy Efficiency Design Index (EEDI) for new ships building and the Energy Efficiency Operational Indicator (EEOI) for ship operation, thus an accurate estimation of added resistance of ships advancing in waves has become necessary. In the present study, OpenFOAM, computational fluid dynamics libraries of which source codes are opened to the public, was used to calculate the added resistance and motions of the KCS. Unstructured grid using a hanging-node and cut-cell method was used to generate dense grid around a wave and KCS. A dynamic deformation mesh method was used to consider the motions of the KCS. Five wavelengths from a short wavelength (${\lambda}/LPP=0.65$) to a long wavelength (${\lambda}/LPP=1.95$) were considered. The added resistance and the heave & pitch motions calculated for various waves were compared with the results of model experiments.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.3
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• pp.240-245
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• 2015

In this study, experiments were performed using a model of a very large crude oil carrier (VLCC), which is a typical blunt ship, in a wave-making towing tank. The aim of the experiments was to determine the effect of added resistance in waves on the various operating conditions of a VLCC. An analysis of the results was conducted to determine the characteristics of resistance performance in waves. In addition, the characteristics of added resistance on a tanker were analyzed under irregular waves based upon the above result. The experimental results showed that added resistance was the highest around ${\lambda}/L=1.0$, and the added resistance increased with the increase of the ship speed. Furthermore, under even keel conditions, the added resistance was higher than that under the trim changes, and the smallest added resistance was measured at the trim by the stern. Based on the experimental results, this study proposes effective operating conditions by analyzing the characteristics of the mean added resistance and the expected extreme response in irregular waves.

• Journal of Ocean Engineering and Technology
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• v.18 no.3
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• pp.40-43
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• 2004

A rational method is presented for estimating the power increase of a ship at sea. A probabilistic approach is applied to determine the weather condition at sea, A comparison is made between some full-scale data and the result of Swift's method. A comparison is also made to find differences among the results of eight kind methods for the wind added resistance of a VLCC in head wind. The mean difference between the results is 7％, in general, for a given relative wind speed.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.2
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• pp.149-159
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• 2017

In this study, the numerical investigation of ship motions and added resistance at constant forward velocity of KVLCC2 model is presented. Finite volume CFD code is used to calculate three dimensional, incompressible, unsteady RANS equations. Numerical computations show that reliable numerical results can be obtained in head waves. In the numerical analyses, body attached mesh method is used to simulate the ship motions. Free surface is simulated by using VOF method. The relationship between the turbulence viscosity and the velocities are obtained through the standard ${\kappa}-{\varepsilon}$ turbulence model. The numerical results are examined in terms of ship resistance, ship motions and added resistance. The validation studies are carried out by comparing the present results obtained for the KVLCC2 hull from the literature. It is shown that, ship resistance, pitch and heave motions in regular head waves can be estimated accurately, although, added resistance can be predicted with some error.

• Journal of the Society of Naval Architects of Korea
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• v.54 no.3
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• pp.258-266
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• 2017

Numerical simulations of turbulent two phase flows around KCS have been performed to investigate effects of trim conditions on ship resistance of KCS in short waves by utilizing waves2foam. The wave lengths of LPP/2 and LPP/4 with 1m and 2m wave heights were imposed at inlet boundary. The resistance reduction at 2m trim by head and the increase of resistance at trims by stern were observed regardless of wave lengths and wave heights. The hull pressure on fore-and-aft rather than wave patterns around bulbous bows was mainly responsible for the total resistance coefficients of KCS in short waves. A phase diagram of contribution of hull pressure to the total resistance coefficients disclosed that the phase of representing the maximum resistance in time history played an important role in the effect of trim conditions on ship resistance of KCS in short waves.

• Journal of Ocean Engineering and Technology
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• v.11 no.2
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• pp.91-99
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• 1997

This paper presents theoretical formulations and numerical computations for predicting first-and second-order hydrodynamic force on a ship advvancing in waves. The theoretical formulation leads to linearized radiation and diffration problems solving the three-dimensional Green function integral equations over the mean wetted body surface. Green function representing a translating and pulsating source potantial for infinite water depth is used. In order to solve integral equations for three dimentional flows using Green function efficiently, the Hoff's method is adopted for numerical calculation of the Green function. Based on the first-order solution, the mean seconder-order forces and moments are obtained by directly integrating second-order pressure over the mean wetted body surface. The calculated items are carried out for analyzing the seakeeping characteristics of Series 60. The calculated items are hydrodynamic coefficients, wave exciting forces, frequency response functions and addd resistance in waves.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.5
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• pp.564-575
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• 2016

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.

• Journal of the Korean Society for Marine Environment & Energy
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• v.19 no.2
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• pp.159-164
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• 2016

It is one of the important processes to predict the resistance of the towed ship when towing a disabled ship on the sea. Besides the basic resistance of hull itself, there are various added resistance, especially the added resistance due to waves can be considered one of the biggest component. In this paper, the algorithm which predict the added resistance due to waves of a disabled ship by theoretical analysis method of ISO 15016 standard was established, and realized as a computer program. The calculated result for an example ship was compared with existing standard one, and it is considered that this algorithm and computer program are appropriate to use for predicting the resistance and towing force of the disabled ship actually.

• Ocean Systems Engineering
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• v.6 no.4
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• pp.305-324
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• 2016

Wave load prediction at zero forward speed using finite depth Green function is a well-established method regularly used in the offshore and marine industry. The forward speed approximation in deep water condition, although with limitations, is also found to be quite useful for engineering applications. However, analysis of vessels with forward speed in finite water depth still requires efficient computing methods. In this paper, a method for analysis of wave induced forces and corresponding motion on freely floating three-dimensional bodies with low to moderate forward speed is presented. A finite depth Green function is developed and incorporated in a 3D frequency domain potential flow based tool to allow consideration of finite (or shallow) water depth conditions. First order forces and moments and mean second order forces and moments in six degree of freedom are obtained. The effect of hull flare angle in predicting added resistance is incorporated. This implementation provides the unique capability of predicting added resistance in finite water depth with flare angle effect using a Green function approach. The results are validated using a half immersed sphere and S-175 ship. Finally, the effect of finite depth on a tanker with forward speed is presented.