• Journal of Power System Engineering
• /
• v.11 no.1
• /
• pp.98-106
• /
• 2007

This paper presents a statistical prediction procedure for the propeller racing of ships with twin screw propellers sailing in ocean waves. The propeller racing is one of the most important factors of seakeeping qualities in relation to the safety of main engine and shafting system. It is especially significant key word for designing the twin-screw-propeller-type ship in view of allowable maximum propeller diameter etc.. In former studies, the propeller racing generally means the situation (propeller exposed) in which the relative motion amplitude between ship hull and wave surface would exceed a depth of point in rotary disk propeller. Therefore, it seems that the magnitude of the amplitude and its exceeding frequency have been examined as a principal subject of study as usual. However, the time during which the amplitude exceeds a depth of point must be also one of most important factor affecting the trend of propeller racing. This paper proposes a simply practical method for estimating the time lasting of exposed propeller related to twin screw propeller racing in rough confused seas on the basis of the statistics. Then, it is confirmed that the practical method is useful and convenience for considering the propeller racing in the stage of the basic design.

• Journal of Navigation and Port Research
• /
• v.34 no.5
• /
• pp.319-324
• /
• 2010

For the purpose of technological analysis in the marine accidents and their prevention, IMO have made it obligatory to load VDR which is similar to the black box in aircraft. However, in case of body sinkage, capsizing, stranding and plunging which are almost 10% of marine accidents, it is difficult to take out the necessary data from the VDR in order to analyze the cause of them. Therefore, this paper apply the navigation dangerousness evaluation technology to the VDR to improve its performance. And we suggest that the vertical acceleration which is one of the factors for evaluating seakeeping performance of a ship is to be added in the existing VDR record data recommended by IMO.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2018.05a
• /
• pp.41-42
• /
• 2018

This study is about the prediction of ship's roll motion characteristic which has been used for evaluating ship's seakeeping performance. In order to obtain the ship's roll RAO during voyage, this paper utilized machine learning-based surrogate model. By comparing the prediction result data of surrogate model with test data, we suggest the best approximation technique and data sampling interval of the surrogate model appropriate for predicting the ships' roll motion characteristic.

• Journal of Korean Port Research
• /
• v.7 no.1
• /
• pp.89-114
• /
• 1993

ICLL 66 is the most widely ratified instrument of the IMO and is, along with the International Convention on Safety of life at Sea (SOLAS), the primary document setting forth internationally agreed ship safety standards. ICLL 66 set freeboard requirement based on experience gained from the first Load Line Convention in 1930 and on contemporary developments in ship design. Reexamination of ICLL 66 is indicated by the proliferation of novel ship designs for which it lacks adequate regulations and by significant advancements in analytical seakeeping and deck wetness prediction techniques now available to the designer. In this paper, the Freeboard Advisory Group reviews these issues against the changing climate of the marine industry and maritime administrations, discusses the state of the art in analytical seakeeping programs, and outlines a series of recommendations for the establishment of a new international load line convention for the next century. The steps needs for an international program at IMO are discussed and a new convention is proposed.

• Journal of the Society of Naval Architects of Korea
• /
• v.31 no.4
• /
• pp.51-57
• /
• 1994

In this study, the method for calculation of the frequency transfer function of motions based on the multi-directional waves in the analysis of a full-scale seakeeping trials is presented. For calculation of the frequency transfer function in the directional waves, Takezawa's inverse estimation method was introduced and the frequency ranges were divided into three parts in order to consider following seas. To confirm the validity of this method, the numerical simulation was executed. Those results show that analysis method of the multi-directional waves is more reliable than that of one directional waves, and confirm the possibility of applying this method to the full-scathe seakeeping trials.

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

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.13 no.1
• /
• pp.260-277
• /
• 2021

The appropriate radiation conditions of ship motion problem with advancing speed in frequency domain are investigated from a theoretical and practical point of view. From extensive numerical experiments that have been conducted for evaluation of the relevant radiation conditions, a hybrid radiation technique is proposed in which the Sommerfeld radiation condition and the free surface damping are mixed. Based on the comparison with the results of the translating and pulsating Green function method, the optimal damping factor of the hybrid radiation technique is selected, and the observed limitations of the proposed hybrid radiation technique are discussed, along with its accuracy obtained from the numerical solutions. Comparative studies of the forward-speed seakeeping prediction methods available confirm that the results of applying the hybrid radiation technique are relatively similar to those obtained from the translating and pulsating Green function method. This confirmation is made in comparisons with the results of solely applying either the free surface damping, or the Sommerfeld radiation condition. By applying the proposed hybrid radiation technique, the wave patterns, hydrodynamic coefficients, and motion responses of the Wigley III hull are finally calculated, and compared with those of model tests. It is found that, in comparison with the model test results, the three-dimensional Rankine source method adopting the proposed hybrid radiation technique is more robust in terms of accuracy and numerical stability, as well as in obtaining the forward speed seakeeping solution.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2004.11a
• /
• pp.61-70
• /
• 2004

This paper treats optimal route assessment system at seaway based on weather forecasting and wave measurement through observation. Since early times. captain & officer have been sailing to select the optimum route considering the weather ana ship status condition empirically. However. it is rare to find digitalized onboard route support system whereas weather fax or wave and swell chart are utilized for the officer. based on officer's experience. In this paper, optimal route assessment system which is composed of voyage efficiency and safety component is introduced. Optimum route minimized ETA (estimated time of arrival) ana fuel consumption is evaluated for efficient voyage considering speed loss and power increase based on wave added resistance of ship. In the view point of safety, seakeeping prediction is performed based on 3 dimensional panel method. Basically. the weather forecast is assumed to be prepared previously in order to operate this system.

• Journal of Navigation and Port Research
• /
• v.28 no.10 s.96
• /
• pp.833-841
• /
• 2004

This paper treats optimal route assessment system at seaway based on weather forecasting and wave measurement through observation Since early times, captain & officer have been sailing to select the optimum route considering the weather and ship status condition empirically. However, it is rare to find digitalized onboard route support system whereas weather fax or wave and swell chart are utilized for the officer, based on officer's experience. In this paper, optimal route assessment system which is composed of voyage efficiency and safety component is introduced. Optimum route minimized ETA(estimated time of arrival) and fuel consumption is evaluated for efficient voyage considering speed loss and power increase based on wave added resistance of ship. In the view point of safety, seakeeping prediction is performed based on 3 dimensional panel method. Basically, the weather forecast is assumed to be prepared previously in order to operate this system.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2017.11a
• /
• pp.236-237
• /
• 2017

In this research, experimental seakeeping results of Warped hull form 2 on the regular waves were compared with numerical results of strip method and CFD. In case of ship's speed, there are 3 cases (3.4m/s, 4.6m/s, 5.75m/s) for numerical simulation, and they are belong to semi-planing and planing condition. Consequently, in case of strip method, it is shown that the resonance phenomena occurred from around ${\lambda}/L_{OA}=2$ to 4 and RAO value were significantly higher than that of other. this is different from experimental results. In case of CFD, overall trends were similar with experimental values except there are somewhat excessive RAO values around ${\lambda}/L_{OA}=0.5$ to 2.5. these phenomena is confirmed that it became larger as the ship's speed increased, and it was considered that the error occurred because the number of mesh in vertical direction of wave height at ${\lambda}/L_{OA}=0.5$ to 2.5 were relatively less than those of wave height at ${\lambda}/L_{OA}=2.5$ to 5.2.