• Journal of Ship and Ocean Technology
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• v.7 no.2
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• pp.29-39
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• 2003

A Coanda foil is a high-lift generating device exploiting the phenomena that flow separation is delayed if a high-speed jet is applied tangential to the surface as well known to the aerodynamic fields. In the present study, a Coanda foil with a flap is investigated to seek the possibility of marine application. Model experiments are carried out both in a towing tank and cavitation tunnel and surface pressure distributions, forces and moments acting on the foil are measured at the various angle of attacks and flap angles. The results are also compared to the numerical ones to show good agreements. The results of the present study demonstrate the practical applicability of the Coanda foil in the design of ship control surfaces.

• International Journal of Naval Architecture and Ocean Engineering
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• v.3 no.1
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• pp.105-110
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• 2011

Some research work on CFD computation of ship motions and added resistance in waves for a high speed trimaran is carried out in this paper. The governing equations, Reynolds Averaged Navier-Stokes and continuity equations are discretized by finite volume method. Volume of fluid method is adopted to deal with the nonlinear free surface. The incident waves are generated from the inflow boundary by prescribing a velocity profile resembling flexible flap wavemaker motions, and the outgoing waves are dissipated inside an artificial damping zone located at the rear part of the wave tank. In this paper, the computed results of ship motion and added resistance for a high speed trimaran are presented. The results of seakeeping experiment for the high speed trimaran carried out in CSSRC towing tank are also presented in this paper. Rather good agreements are shown between the computational and experimental results. The work in this paper provides a numerical tool for the study of seakeeping performance of high speed trimarans.

• Bulletin of the Society of Naval Architects of Korea
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• v.10 no.2
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• pp.19-28
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• 1973

This paper deals with a problem for determining the bulbous bow ship from which pertains to the study of the theoretical ship form planing method. In this paper has been determined the bulbous bow ship form which is a similar in geometric particulars with the conventional liner ship G.T.10, 000 by adopting the variable method for finding the optimum ship form by A.Y.C. Lee and the streamline tracing method by T. Inui and P.C. Pien. Each resistance performance is examined by the towing test and is compared with one another. The followings are the outcome of this study: Among the 5 type models, the bulbous bow ship form M.S. B 1120 is the most excellent for the resistance performance. The effect for the wave resistance is very sharp according to the difference of the bottom flattening of theoretical ship form. The optimum value of the bulbous bow for wave resistance can be obtained by the variable method mentioned above, and for the series of(Main hull+Bulb)opt., ${\alpha}=75/25$, the value is $f{\approx}0.11$.

• Journal of Ocean Engineering and Technology
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• v.23 no.1
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• pp.129-134
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• 2009

This paper reports on experimental investigations of self propulsion performance with synthetic (model) ice and refrigerated ice, which were conducted in a typical towing tank and ice tank, respectively. The main purpose of this research was to find the correlation between the selfpropulsion performance with synthetic ice in a typical towing tank and that with refrigerated ice in an ice tank. The different stresses between the synthetic ice and refrigerated ice influenced the self propulsion performance due to different ice and propeller interactions. A further study on the ice property variation for a self propulsion performance comparison is to be conducted in the near future.

• Journal of Navigation and Port Research
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• v.36 no.9
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• pp.707-714
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• 2012

Recently, tug boats are widely used for towing a barge which transports building materials, a large block of a ship, offshore crane, and so on. In order to simulate the dynamics of the coupled towing system correctly, the dynamics of the towline should be well modeled. In this paper, the towline was modeled as the multiple finite elements, and each element was assumed as a rigid cylinder which moves in five degrees of freedom except roll. The external tension and its moment acting on each element of the towline were modeled depending on the position vector's direction. Tugboat's motion was simulated in six degrees of freedom where wave and current effects were included, and towed barge was assumed to move in the horizontal plane only. In order to confirm the mathematical models of the coupled towing systems, standard maneuvering trials such as course changing maneuver, turning circle test and zig-zag test were simulated. In addition, the same trials were simulated when the external disturbances like wave and current exist. As the result, it is supposed that the results might be qualitatively reasonable.

• Journal of the Korean Society of Marine Environment & Safety
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• v.13 no.4
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• pp.71-78
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• 2007

Towing vessels have carried out the important role and service in the maritime industry construction, such as port and sea bridge construction, fairway dredging and sea reclamation etc. Furthermore, tugboat takes the largest portion in number of vessel at the domestic registry and barges as big as the general merchant vessel, which are getting specialized and larger, are in operation. In spite of the increase of marine accidents under this situation, there has been no proper measure for the safe navigation of tugboat in the aspect of a nation. This paper aims to propose the measure for the safe navigation of tugboat according to the frequent marine accident of tugboat with sea bridge. Therefore, we show an example of the sailing schedule and operation checklist based on the analysis of statistics and precedent of marine accident and the investigation of the actual operation state of tugboat in the aspect of a contract of carriage and a personnel setup, which should be checked by the operator of tugboat, to pass through sea bridge safely and propose the safe traffic supporting system based on electronic chart system to improve the safe navigation of tugboat.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.55 no.1
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• pp.7-19
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• 2019

This study was conducted in order to improve opening efficiency of the miniaturized small-scale net for anchovy boat seine gear to reduce the fleet size. Field experiment was performed to observe geometry of nets by catcher boats. When the distance between the two ships was 150, 300 and 450 m and the speed of towing nets was 0.6, 0.9, and 1.2 kt, the vertical opening and actual opening of each part of the miniaturized small-scale net was as follows: the front part of the wing net, 6.8-9.5 m, 45-63%; the middle part of the wing net, 16.1-30.7 m, 34-65%; the entrance of the inside wing net, 21.6-41.2 m, 44-84%; the square and bosom, 17.4-34.0 m, 38-75%; the entrance of the body net, 16.5-29.4 m, 36-64%; the entrance of the bag net, 14.5-21.9 m, 70-106%; the flapper, 6.7-7.7 m, 81-83%, and the end of the bag net, 8.6-10.9 m, 64-81%. The tension of towing nets was measured to be 2,734-6,812 kg approximately, which indicates that the fleet can tow nets with 350 hp, the standard engine horse power. The fishing operation time was shortened comparing to existent net with the large-scale buoy attachment operation. It was also possible to operate the ship without fish detecting boat.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.32 no.3
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• pp.273-285
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• 1996

Generally, the flow around the ship's hull often appear 3-dimensional separation at the bow and stem, and the vortex by this flow affects greatly the resistance propulsive efficiency and maneuverability of the ship. This study is compared the calculated result based on the streamlines calculation method with the experimental result by oil fIlm method to analyze the patterns and characteristics of the flows around the ship's hull of chine form. DTMB Series 62, 4667-1 vessel was selected as a sample ship of chine form and model ship was painted with the mixture of oil-color, paint, and poly wax at the surface of the vessel and tested in the model towing tank of Inha University. The results obtained in this study are listed briefly as follows ; 1. For the single chine form, after $4\frac{1}{2}$ station the streamlines are crossed at the chine line and the streamlines are converted to the vortex follow the chine line. 2. For the single chine form, the vortex appered increases and severely in and arround the stern. 3. The approximate streamlines for the ship's hull of chine form can be assigned by the use of the Watanabe's basic transformation formular.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.1
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• pp.364-379
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• 2019

Wave-induced ship motion and load responses are usually investigated on the assumption that the incident waves are long-crested. The realistic sea waves are however short-crested irregular waves. Real practice reveals that the ship motion and load responses induced by short-crested waves are different from those induced by long-crested waves. This paper aims to conduct a comprehensive study on ship motions and loads in different wave fields. For this purpose, comparative studies by small-scale model towing tank test and large-scale model sea trial are conducted to experimentally identify the difference between ship motions and loads in long-crested and short-crested irregular waves. Moreover, the influences of directional spreading function of short-crested waves on ship motions and loads are analyzed by numerical seakeeping calculation. The results and conclusions obtained from this study are of great significance for the further extrapolation and estimation of ship motions and loads in short-crested waves based on long-crested wave response results.

• Journal of the Society of Naval Architects of Korea
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• v.40 no.5
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• pp.1-9
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• 2003

To predict the powering performance of full scale ships from the towing tank tests, resistance, propeller open water and self-propulsion tests are conducted. Model tests inevitably include the experimental error defined as the sum of two types of uncertainties, bias and precision errors. The induced errors in each element of model test are propagated through various routes and correlated with one another. The correlation coefficients are very important in the uncertainty analysis. The coefficient gives a direction(increase or decrease) for a value of error in individual elements. If the coefficient is not used accurately, the error bounds of the individual elements are overestimated or underestimated. In this study, the new methodology is applied to the uncertainty analysis of HMRI's towing tank tests, thus error bounds of each element is suggested and verified by several repetitive experiments.