• Journal of the Korean Institute of Navigation
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• v.24 no.3
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• pp.103-111
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• 2000

From a ship's safe operation point of view, it is very important to estimate the navigational safety in a seaway. The seakeeping performance can be defined as the ability of a ship to go to sea, and to accomplish its missions successfully and safely even in adverse environmental conditions. There are several factors presently adopted for evaluating seakeeping performance. But a hardware of the system considering all these factors has not been developed since some of them can not be measured by sensors. In this paper, a synthetic method of evaluating navigational safety is developed by measuring the vertical and lateral acceleration. An experiment by using real measuring carried out on board the T/S 'HANNARA' The equipment was measured every 4 hours for more than 30 minutes the acceleration by accelerometer, analyzed its acceleration values and calculated navigational dangerousness. As the results of this on board experiment, the system is carried conviction to be useful as evaluating seakeeping performance.

• 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.

• 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.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.6
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• pp.641-654
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• 2017

The KVLCC2 and its modified hull form were investigated in regular head waves using Unsteady Reynolds Averaged Navier-Stokes (URANS) methods. The modified KVLCC2 (named KWP-bow KVLCC2) is designed for reducing wave reflection from the bow. Firstly, the original KVLCC2 is studied for verification of the present code and methodology and the computed time history of total resistance and 2DOF motions (heave and pitch) for the selected two wave length conditions are directly compared with the results obtained from KRISO towing tank experiment under the identical condition. The predicted added resistance, heave and pitch motion RAOs show relatively good agreement with the experimental results. Secondly, the comparison of performance in waves between KVLCC2 and KWP-bow KVLCC2 is carried out. We confirmed that newly designed hull form shows better performances in all the range of wave length conditions through both the computation and the experiment. The present URANS method can capture the difference of performance in waves of the two hull forms without any special treatment for short wave length conditions. It can be identified that KWP-bow KVLCC2 gives about 8% of energy saving in sea state 5 condition.

• Journal of the Society of Naval Architects of Korea
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• v.60 no.5
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• pp.305-319
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• 2023

This study focuses on measuring the relative wave elevation around the KSUPRAMAX-O ship and comparing it with numerical analysis results (potential and computational fluid dynamics). The relative wave elevation is a good indicator of the pressure distribution on the ship's surface, which is affected by the ship's motion, incident waves, and distributed waves. Prior to measuring the relative wave elevation, a comparative test was conducted on resistance type, capacitance type, and ultrasonic type wave probe to measure the relative wave elevation, and it was confirmed that the resistance type wave probe was suitable for measuring the relative wave elevation. A model test was performed at low speed and design speed using resistance type wave probe and compared with the results of numerical analysis result. As for the motion response, it was confirmed that the result of experiments and the result of the numerical analysis were in good agreement. The relative wave elevation showed a similar trend between the experiment and the computational fluid dynamics, but the potential analysis result showed a difference from the experiment in design speed.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.4
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• pp.397-402
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• 2013

In this study, numerical hull form development of a platform supply vessel, a full scale with the overall length of 26.75m, was performed to predict a bare-hull resistance and a large scale of model tests with a 1/10 scaled model were conducted to verify the success of numerical results. Numerical analysis on heave and pitch motion as a function of encounter frequency and ship's speed for the prediction of seakeeping characteristics are also presented. The experiment results of resistance agreed well with numerical analysis. As a result in the motion response characteristics, the heave RAO indicates high values with the range of encounter frequency 1.8~2.0. The Pitch RAO indicates high motion response characteristics at Beaufort scale No. 3 and 4 in rough seas.

• International Journal of Naval Architecture and Ocean Engineering
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• v.6 no.4
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• pp.1130-1147
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• 2014

Large size ships have a very flexible construction resulting in low resonance frequencies of the structural eigen-modes. This feature increases the dynamic response of the structure on short period waves (springing) and on impulsive wave loads (whipping). This dynamic response in its turn increases both the fatigue damage and the ultimate load on the structure; these aspects illustrate the importance of including the dynamic response into the design loads for these ship types. Experiments have been carried out using a segmented scaled model of a container ship in a Seakeeping Basin. This paper describes the development of the model for these experiments; the choice was made to divide the hull into six rigid segments connected with a flexible beam. In order to model the typical feature of the open structure of the containership that the shear center is well below the keel line of the vessel, the beam was built into the model as low as possible. The model was instrumented with accelerometers and rotation rate gyroscopes on each segment, relative wave height meters and pressure gauges in the bow area. The beam was instrumented with strain gauges to measure the internal loads at the position of each of the cuts. Experiments have been carried out in regular waves at different amplitudes for the same wave period and in long crested irregular waves for a matrix of wave heights and periods. The results of the experiments are compared to results of calculations with a linear model based on potential flow theory that includes the effects of the flexural modes. Some of the tests were repeated with additional links between the segments to increase the model rigidity by several orders of magnitude, in order to compare the loads between a rigid and a flexible model.