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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Society of Naval Architects of Korea
Journal Basic Information
Journal DOI :
The Society of Naval Architects of Korea
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Volume & Issues
Volume 50, Issue 6 - Dec 2013
Volume 50, Issue 5 - Oct 2013
Volume 50, Issue 4 - Aug 2013
Volume 50, Issue 3 - Jun 2013
Volume 50, Issue 2 - Apr 2013
Volume 50, Issue 1 - Feb 2013
Selecting the target year
Development and Application of an Open Water Test System for Azimuth Thrusters
Lee, Young-Jin ; Rhyu, Seong-Sun ; Seo, Jong-Soo ; Lew, Jae-Moon ;
Journal of the Society of Naval Architects of Korea, volume 50, issue 4, 2013, Pages 199~205
DOI : 10.3744/SNAK.2013.50.4.199
To research and develop an azimuth thruster, the new type of open water test dynamometers to measure thrust, torque, total thrust and duct force are designed and manufactured by Samsung Ship Model Basin(SSMB). A compact servomotor to be accurately controlled is connected to precise spiral bevel gear through shafting system combined by couplings and main shafts. The dynamometers have shown excellent linearity and repeatability for all components of forces and a torque. Also, the open water tests have been successfully performed to show the performance of the system. In near future, it is expected that the device can be used for the study of scale effects and development of azimuth thrusters.
Study on Prediction and Control of Wind-Induced Heel Motion of Cruise Ship
Kim, Jae-Han ; Kim, Yonghwan ; Kim, Yong-Soo ;
Journal of the Society of Naval Architects of Korea, volume 50, issue 4, 2013, Pages 206~216
DOI : 10.3744/SNAK.2013.50.4.206
The present study considers the prediction of wind-induced heel of cruise ship and its stabilization. Wind load in ocean exerts on the surface of superstructure of cruise ship, which causes the heel moment on the ship. The calculation of wind load starts from choosing wind speed profile, so that the logarithmic wind profile model is applied in this study. Heel moment by wind load is calculated by adopting approximate formulation and applied to the ship motion analysis in time domain. Motion stabilizers, such as stabilizing fin and U-tube tank, are considered to reduce the heel effect as well as excessive roll motion. From this study, it is expected that the present method can be applied to the prediction and stabilization of the heel motion of cruise ships.
Wet Damping Estimation of the Segmented Hull Model using the Random Decrement Technique
Kim, Yooil ; Park, Sung-Gun ;
Journal of the Society of Naval Architects of Korea, volume 50, issue 4, 2013, Pages 217~223
DOI : 10.3744/SNAK.2013.50.4.217
This paper presents the wet damping estimation of the segmented hull model using the random decrement technique together with the continuous wavelet transform. The tested 16 sea states are grouped together based on the speed of the ship in order to figure out the possible influence of the ship speed on the damping ratio. The measured time histories of vertical bending moment for each tested sea state were processed with random decrement technique to derive the free decay signal, from which the damping ratios are estimated. Also, the autocorrelation functions of the filtered signal were calculated and comparison was made with the free decay signal obtained from the random decrement technique. Then the wet damping ratios for each sea state group, as well as precise wet natural frequencies, are estimated by using continuous wavelet transform. It turned out that the wet natural frequencies derived from the measured signal did not show any significant discrepancy compared with those obtained by wet hammering test, whereas the damping ratio did. It was considered that the discrepancy of the damping ratio between in calm and moving water may be attributed to the viscous effects caused by dramatically different flow pattern and relative velocity between the vibrating structure and surrounding fluid particles.
Natural Frequency of 2-Dimensional Heaving Circular Cylinder: Time-Domain Analysis
Kim, Ki-Bum ; Lee, Seung-Joon ;
Journal of the Society of Naval Architects of Korea, volume 50, issue 4, 2013, Pages 224~231
DOI : 10.3744/SNAK.2013.50.4.224
The concept of the natural frequency is useful for understanding the characters of oscillating systems. However, when a circular cylinder floating horizontally on the water surface is heaving, due to the hydrodynamic forces, the system is not governed by the equation like that of the harmonic one. In this paper, in order to shed some lights on the more correct use of the concept of the natural frequency, a problem of the heaving circular cylinder is analyzed in the time domain. The equation of motion, an integro-differential equation, was derived following the fashion of Cummins (1962), and its coefficients including the retardation function were obtained using the numerical solution of Lee (2012). The equation was solved numerically, and the experiment was also carried out in the CNU flume. Using our numerical and experimental results, the natural frequency was defined as its average value given by the motion data excluding those of the initial stage. Our results were then compared with those of the existing investigations such as Maskell and Ursell (1970), Ito (1977) and Yeung (1982) as well as the newly obtained results of Lee (2012). Comparison showed that the natural frequency obtained here agrees well with that of Lee (2012), which was found through the frequency domain analysis. It was also shown that the approximation of heaving motion by a damped harmonic oscillation, which was regarded as suitable by most previous investigators, is not physically suitable for the reason that can be clearly shown through comparing the shape of MCFRs(Modulus of Complex Frequency Response). Furthermore, we found that although the previous approximations yield the damping ratio significantly different from our result the magnitude of natural frequency is not much different from our result.
Numerical Prediction of Ship Motions in Wave using RANS Method
Park, Il-Ryong ; Kim, Jin ; Kim, Yoo-Chul ; Kim, Kwang-Soo ; Van, Suak-Ho ; Suh, Sung-Bu ;
Journal of the Society of Naval Architects of Korea, volume 50, issue 4, 2013, Pages 232~239
DOI : 10.3744/SNAK.2013.50.4.232
This paper provides the structure of a Reynolds Averaged Navier-Stokes(RANS) based simulation method and its validation results for the ship motion problem. The motion information of the hull computed from the equations of motion is considered in the momentum equations as the relative fluid motions with respect to a non-inertial coordinates system. A finite volume method is used to solve the governing equations, while the free surface is captured by using a two-phase level-set method and the realizable k-
model is used for turbulence closure. For the validation of the present numerical approach, the numerical results of the resistance and motion tests for DTMB 5415 at two ship speeds are compared against available experimental data.
Comparative Study on the Motion Responses for a 40ft Class Cruise Leisure Boat
Kim, Dong-Jin ; Rhee, Key-Pyo ; Yum, Deuk-Joon ; Zhang, Yang ;
Journal of the Society of Naval Architects of Korea, volume 50, issue 4, 2013, Pages 240~247
DOI : 10.3744/SNAK.2013.50.4.240
Hydrodynamic characteristics of a planing craft are very sensitive to the hull form variations, especially when the craft navigates with high-speed. Therefore, we need to verify hydrodynamic performances of the craft during the process of hull form design. In this paper, motion performances of a 40ft class cruise leisure boat are evaluated by both model tests and theoretical analyses using two different methods. Model tests are carried out at calm sea and regular wave conditions using high speed towing carriage installed in SNU towing tank. Theoretical methods used are a empirical method proposed by Martin (1976) and a potential method based on Rankine panel (DNV, 2010). The results from the theoretical methods are compared with and verified by those of model tests. Results of empirical formula showed somewhat larger motion RAOs and resonant frequencies than those of model tests. Potential based method showed even larger discrepancies with the model test results. From the analyses of comparison results, we could confirm the limitation of each theoretical method and suggest the way of improvement for the better prediction of motion performances.
Algorithm for Performance Analysis of Vane-Wheel using Panel Method
Seok, Woo-Chan ; Suh, Jung-Chun ;
Journal of the Society of Naval Architects of Korea, volume 50, issue 4, 2013, Pages 248~254
DOI : 10.3744/SNAK.2013.50.4.248
In this paper, we establish an analysis algorithm and a design procedure for a Vane-Wheel which is a freely rotating device behind a propeller, by using a panel method. Vane-Wheel`s function is to extract energy from the propeller slipstream in turbine part which is inner part of the Vane-Wheel, and convert this energy into an additional propulsive thrust in propeller part which is outer part of the Vane-Wheel. Two parts must satisfy torque balance and thrust has to act to the ship`s forward direction. A Vane-Wheel has large interaction effect with propeller since it is placed behind of the propeller. Therefore, in order to consider interaction effect correctly, incoming velocity to the Vane-Wheel in a circumferential mean wake was calculated considering induced velocity from propeller to the Vane-Wheel. Likewise, incoming velocity to the propeller was calculated considering induced velocity from the Vane-Wheel to the propeller. This process is repeated until a converged result is obtained.
Assessment of Ultimate Longitudinal Strength of a VLCC considering Kinematic Displacement Theory
Choung, Joonmo ; Nam, Ji-Myung ; Tayyar, Gokhan Tansel ; Yoon, Sung-Won ; Lee, Kangsu ;
Journal of the Society of Naval Architects of Korea, volume 50, issue 4, 2013, Pages 255~261
DOI : 10.3744/SNAK.2013.50.4.255
This paper presents prediction of ultimate longitudinal strength of a VLCC, "Energy Concentration" for which many benchmark studies have been carried out, based on kinematic displacement method proposed by Tayyar and Bayraktarkatal (2012). Kinematic displacement theory provides semi-analytical solution of average compressive strengths for various kinds of stiffened panels. The accuracy of average compressive strengths obtained from formulas of CSR(common structural rules) for tankers and kinematic displacement method are discussed in the fore part of this paper. Hull girder ultimate strengths using Smith method are also compared for different average compressive strengths. By comparing them with other benchmark results, it is concluded that the new method provides lower bounds, because hull girder strengths under the sagging and hogging moment conditions approach nearly lower bounds.
Development of Shipbuilding Execution Scheduling Support System using Mobile Device : A Case Study for a Panel Block Assembly Shop
Hwang, Inhyuck ; Song, Jungkyu ; Back, Myunggi ; Ryu, Cheolho ; Lee, Kwangkook ; Shin, Jong Gye ;
Journal of the Society of Naval Architects of Korea, volume 50, issue 4, 2013, Pages 262~271
DOI : 10.3744/SNAK.2013.50.4.262
Owing to the development of mobile communication technology during the last a few years, the number of users of mobile devices such as the smartphone and the tablet PC has increased rapidly. As a result, the range of applications of the mobile devices has also been greatly expanded from an application for the convenience of daily life to an application for assisting the operations of industrial fields. Especially, portability of mobile devices can provide great help in collecting and using information on the production site. In shipbuilding production processes, it is difficult to collect changes of circumstance in the field and reflect the changes to schedule due to the low production automation rate and frequent changes in schedule. In this study, we propose a system to solve the problems of shipbuilding production processes such as the ones described above by using mobile devices. First of all, we organize the production information and production processes of the panel line through the analysis of shipyard panel line operations. Next, we have developed a system that can support the production execution plan of the panel line and monitor the production processes in the field. The system was developed utilizing application virtualization to allow access to the system from various platforms of mobile devices and PC`s. The system was implemented using ooCBD methodology considering the future expansion of the system and ease of maintenance.