• Journal of Fisheries and Marine Sciences Education
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• v.28 no.4
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• pp.1024-1030
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• 2016

This study gives the vertical motion analysis due to changes in Submerged shape of Multi-Purpose Small Floating Body in irregular waves using the commercial code(MAXSURF v.20) based on the Panel method. To verify the commercial code prior to the analysis, we guarantees the reliability of this paper's results using the commercial code by comparing with the results of experimental results on Catamaran. The anlysis conditions are ITTC wave spectrum, each encounter angle. Finally, we analyze the result of ship's response spectra for vertical motions.

• Journal of the Korean Institute of Navigation
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• v.15 no.1
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• pp.49-65
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• 1991

It is of great importance for any vessel under way, especially in rough sea, to be maneuvered safely with proper seakeeping performance. In this paper, the author aims to develope a navigational safety evaluation system in rough sea by analyzing ship's with the theory of wave spectrum using random process analysis and the theory of evaluating the seakeeping performance. The scope and the method of this study are as follows ; (1) Modelized typhoon mathematically to represent the sea condition in rough sea. (2) Estimated sea conditions by getting wave spectrum, supposing that the wave by typhoon is fully developed short crest irregular wave. (3) Defined evaluation factor of vessel's seakeeping performance and obtained response amplitude operators thereby. (4) Obtained the response spectrum of factors on seakeeping performance. (5) Defined and obtained evaluation index, dangerousness, relative and maximum dangerousness of factors on seakeeping performance. (6) Analyzed the calculated dangerousness of evaluation index and picked the vertical acceleration out of 7 factors as the presentative factor on seakeeping performance. (7) Carrid out the judgement of danger by obtaining dangerousness value according to steaming hour, course alteration and speed change. By synthesizing the above items, the authors suggests a computer model of navigational safety evaluation system and examined the validity of the model by computer simulation.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.1
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• pp.25-34
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• 2017

The concentric dual-buoy Wave Energy Converter (WEC), which consists of external buoy (hallow-cylinder) with toroidal appendage and cylindrical internal buoy within the moon-pool is suggested in this research and its performance in various wave conditions is studied. The Linear Electric Generator (LEG), consisting of a permanent magnet and coils, is used as a direct Power Take-Off (PTO) system. To maximize the electrical energy extracted from the PTO system, the relative heave motions between the dual buoys must be highly amplified by the multiple resonance phenomena of dual-buoy and internal-fluid motions. The high-performance range can be widened by distributing those natural frequencies with respect to the peak frequency of the wave spectrum. The performance of the newly developed dual-buoy WEC was measured throughout the systematic 1:5.95-model test in regular and irregular waves conducted in a wave tank at Seoul National University. The model-test results are also validated by an independently developed numerical method.

• 한국방재학회:학술대회논문집
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• 2007.02a
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• pp.168-171
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• 2007

The stability of a typical rubble mound breakwater defenced by a submerged structure is investigated using hydraulic experiments. Incident irregular waves are obtained from the Bretschneider-Mistuyasu spectrum. Experiments are carried out for different spacings between two breakwaters (X/d=2-3) and for different relative widths (B/h=0.7-3.0) of the submerged structure. It is observed that a submerged structure of (B/h) of 0.7-3.0 constructed at a seaward distance (X/d) of 2-3 breaks all the incident waves and dissipates energy and breakwater.

• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.4
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• pp.291-297
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• 2015

The wave spectrum was generated from wave data measured at the Chagwi-do site in Jeju, where a 10MW class floating wave-offshore wind hybrid power generation system will be installed. The latching control technology (Sheng et al.[2015]) was applied in order to improve the extracted power from WEC (Wave Energy Converter), which is heaving in corresponding irregular waves. The peak period as a representative value of irregular waves was used when we determined the latching duration. From the numerical results in the time-domain analysis, the latching control technology can significantly improve the extracted power about 50%.

• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.2
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• pp.153-159
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• 2012

This study gives the vertical motion analysis in multi-directional irregular waves using a commercial code(MAXSURF v.16) based on linear strip theory for a training ship. To verify the commercial code prior to the analysis, we guarantees the reliability of this paper's results using the commercial code by comparing with the results(Flokstra, 1974) of same hull and experimental conditions on a Panamax container. The analysis conditions are Beaufort wind scale No. 5($\bar{T}=5.46$, $H_{1/3}=2m$) based on ITTC wave spectrum, encounter angle Head & bow seas($150^{\circ}$) and Froude number Fn=0.257. Finally, we calculates heave RAO, pitch RAO and obtains the result of ship's response spectra for heave and pitch motions. In the motion response spectrum under the multi-directional irregular waves, heave motion reacts slightly high in short-crested waves and pitch motion reacts high in long-crested waves.

• Journal of Ocean Engineering and Technology
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• v.27 no.6
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• pp.90-94
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• 2013

This paper reports the results obtained for there flection and transmission coefficients on rubble mound breakwaters in Busan Yacht Harbor. A2D physical model test was conducted in the wave flume at the Coastal Engineering Research Laboratory at Pusan National University, Busan, South Korea. In this study, physical model tests were completed to further our understanding of the hydrodynamic processes that surround a rubble mound structure subjected to irregular waves. In particular, the reflection and transmission coefficients, as well as the spectrum transformation, were analyzed. This analysis suggests that with an increase in wave height around a rubble mound, the reflection coefficient drastically increases at each water level (HHW or MSL or LLW). Moreover, when the water level changes from HHW to LLW, the reflection coefficient is suddenly reduced. A further result of the analysis is that the transmission coefficient strongly drops away from the rear of the structure. Finally, in regard to the rubble mound breakwater in Busan Yacht Harbor, a consideration of the reflection and transmission coefficients plays an important role in the design.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.4 no.2
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• pp.72-82
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• 1992

To accurately estimate nearshore current in shallow water regions. it is necessary to investigate the irregular wave transformation characteristics and radiation stress produced by random sea waves. This research is to investigate the application or the individual wave Analysis Method. the Component Wave Analysis Method and Representative Wave Analysis Method in the shallow water region. These methods were estimated by wave shallowing transformation when the waves propagate from deep water to shallow water region b)r generating regular waves, two component waves and irregular waves (Bretschneider-Mitsuyasu type). That is, the Indivisual Wave Analysis Method is to investigate from the viewpoint of shallow water transformation of wave statistical characteristics and their zero-down-crossing waves (wave height period and wave celerity). And the component Wave Analysis Method is to investigate from the view point of shallow water transformation of basic frequency component wave and their interference frequency component wave. In addition, this research is to compare the measured mean water level elevation with the calculated one from radiation stress of irreguar waves that is assumed in the three methods above.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 1995.04a
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• pp.65-92
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• 1995

The final aim of our research project is a study on assessment of automatic steering system of ships in open seas. In order to achieve this aim we need to know the characteristics of each component of the system and also to know the characteristics of disturbance to ship dynamcis. In this paper we provide calculation method of irregular disturbance to ships in autopilot navigation in open seas and also show calculation examples about two kinds of ship ore carrier and fishing boat. The disturbance consists of irregular wave and random wind, The disturbance is calculated as equivalent yaw angular velocity. Each spectrum and time history of disturbance are reasonably evaluated. Further investigation concerning to performance index of autopilot system and energy loss related to automatic course keeping will be dealt with in another paper,

• Journal of the Korean Institute of Navigation
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• v.19 no.2
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• pp.1-12
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• 1995

The final aim of our research project is a study on assessment of automatic steering system of ships in open seas. In order to achieve this aim, we need to know the characteristics of each component of the system, and also to know the characteristics of disturbance to ship dynamics. In this paper, we provide calculation method of irregular disturbance to ships in autopilot navigation in open seas, and also show calculation examples about two kinds of ship, ore carrier and fishing boat. The disturbance consists of irregular wave and random wind. The disturbance is calculated as equivalent yaw angular velocity. Each spectrum and time history of disturbance are reasonably evaluated. Further investigation concerning to performance index of autopilot system and energy loss related to automatic course keeping, will be dealt with in another paper.