Go to the main menu
Skip to content
Go to bottom
REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
International Journal of Naval Architecture and Ocean Engineering
Journal Basic Information
Journal DOI :
The Society of Naval Architects of Korea
Editor in Chief :
Volume & Issues
Volume 4, Issue 4 - Dec 2012
Volume 4, Issue 3 - Sep 2012
Volume 4, Issue 2 - Jun 2012
Volume 4, Issue 1 - Mar 2012
Selecting the target year
A numerical simulation for reduction of rudder cavitation with gap flow blocking bars
Oh, Jung-Keun ; Lee, Seung-Hee ; Kim, Sang-Hyun ; Seo, Dae-Won ;
International Journal of Naval Architecture and Ocean Engineering, volume 4, issue 2, 2012, Pages 71~82
DOI : 10.3744/JNAOE.2012.4.2.071
In recent practices, a half circular prismatic bar protruding beyond the concave surface of the horn facing the gap has been formed along the centerplane of a rudder to lessen the gap flow between the horn and the movable portion of the rudder system. If a flow through the gap of a rudder is reduced considerably through this approach, previous numerical studies indicate that not only the gap flow but also the rudder cavitation can be noticeably diminished. In the present study, numerical simulations on two-dimensional rudder sections were performed to show that the blocking ability of the single centre bar can be improved by the proper choice of sectional shape. Moreover, a pair of blocking bars attached symmetric to the centerplane on the opposite convex surface of the movable portion is suggested in the study as well, to circumvent the difficulties arising from the practical application of the single centre bars. The bars are placed near the outer edges of the gap easily accessible at the maximum rudder angle to allow simple installation of the device during a maintenance period of a ship. It is found that the pair of blocking bars further improves the blocking effects and application to a practical three-dimensional rudder also backs up the fact.
Investigation of structural responses of breakwaters for green water based on fluid-structure interaction analysis
Lee, Chi-Seung ; Heo, Haeng-Sung ; Kim, Young-Nam ; Kim, Myung-Hyun ; Kim, Sang-Hyun ; Lee, Jae-Myung ;
International Journal of Naval Architecture and Ocean Engineering, volume 4, issue 2, 2012, Pages 83~95
DOI : 10.3744/JNAOE.2012.4.2.083
In the present study, the structural response of breakwaters installed on container carriers against green water impact loads was numerically investigated on the basis of the fluid-structure interaction analysis. A series of numerical studies is carried out to induce breakwater collapse under such conditions, whereby a widely accepted fluid-structure interaction analysis technique is adopted to realistically consider the phenomenon of green water impact loads. In addition, the structural behaviour of these breakwaters under green water impact loads is investigated simultaneously throughout the transient analysis. A verification study of the numerical results is performed using data from actual collapse incidents of breakwaters on container carriers. On the basis of the results of a series of numerical analyses, the pressure distribution of green water was accurately predicted with respect to wave mass and velocity. It is expected that the proposed analytical methodology and predicted pressure distribution could be used as a practical guideline for the design of breakwaters on container carriers.
Acoustical characteristic predictions of a multi-layer system of a submerged vehicle hull mounted sonar simplified to an infinite planar model
Kim, Sung-Hee ; Hong, Suk-Yoon ; Song, Jee-Hun ; Kil, Hyun-Gwon ; Jeon, Jae-Jin ; Seo, Young-Soo ;
International Journal of Naval Architecture and Ocean Engineering, volume 4, issue 2, 2012, Pages 96~111
DOI : 10.3744/JNAOE.2012.4.2.096
Hull Mounted Sonar (HMS) is a long range submerged vehicle's hull-mounted passive sonar system which detects low-frequency noise caused by machineries of enemy ships or submerged vehicles. The HMS needs a sound absorption /insulation multi-layer structure to shut out the self-noise from own machineries and to amplify signals from outside. Therefore, acoustic analysis of the multi-layer system should be performed when the HMS is designed. This paper simplified the HMS multi-layer system to be an infinite planar multi-layer model. Also, main excitations that influence the HMS were classified into mechanical, plane wave and turbulent flow excitation, and the investigations for each excitation were performed for various models. Stiffened multi-layer analysis for mechanical excitation and general multi-layer analysis for turbulent flow excitation were developed. The infinite planar multi-layer analysis was expected to be more useful for preliminary design stage of HMS system than the infinite cylindrical model because of short analysis time and easiness of parameter study.
Damage level prediction of non-reshaped berm breakwater using ANN, SVM and ANFIS models
Mandal, Sukomal ; Rao, Subba ; N., Harish ; Lokesha, Lokesha ;
International Journal of Naval Architecture and Ocean Engineering, volume 4, issue 2, 2012, Pages 112~122
DOI : 10.3744/JNAOE.2012.4.2.112
The damage analysis of coastal structure is very important as it involves many design parameters to be considered for the better and safe design of structure. In the present study experimental data for non-reshaped berm breakwater are collected from Marine Structures Laboratory, Department of Applied Mechanics and Hydraulics, NITK, Surathkal, India. Soft computing techniques like Artificial Neural Network (ANN), Support Vector Machine (SVM) and Adaptive Neuro Fuzzy Inference system (ANFIS) models are constructed using experimental data sets to predict the damage level of non-reshaped berm breakwater. The experimental data are used to train ANN, SVM and ANFIS models and results are determined in terms of statistical measures like mean square error, root mean square error, correla-tion coefficient and scatter index. The result shows that soft computing techniques i.e., ANN, SVM and ANFIS can be efficient tools in predicting damage levels of non reshaped berm breakwater.
Experimental investigation of supercavitating flows
Ahn, Byoung-Kwon ; Lee, Tae-Kwon ; Kim, Hyoung-Tae ; Lee, Chang-Sup ;
International Journal of Naval Architecture and Ocean Engineering, volume 4, issue 2, 2012, Pages 123~131
DOI : 10.3744/JNAOE.2012.4.2.123
When the object is traveling in the water at tremendously high speeds, the cavity forms and grows up at a fore part of the object called cavitator, and the object is eventually enveloped by vaporized water, supercavitation. As a result, the only part of the object in direct contact with the water is the cavitator, so skin-friction drag is significantly reduced. This is why recently supercavitating objects have been interested in many applicable fields. In this study we are focused out attention on supercavitating flows around various shapes of two and three dimensional cavitators. First, general features of supercavitation are examined by analyzing results obtained by the previously developed numerical method. Second, experimental observations are carried out at a cavitation tunnel at the Chungnam National University (CNU CT), and supercavity dimensions are scrutinized.
A study on the fatigue strength characteristics of ship structural steel with gusset welds
Park, Sung-Jo ; Lee, Hyun-Woo ;
International Journal of Naval Architecture and Ocean Engineering, volume 4, issue 2, 2012, Pages 132~140
DOI : 10.3744/JNAOE.2012.4.2.132
This study aims to assess fatigue property by the static overload and average load in the fillet welded joints which is on the ship structural steel having gusset welds. To this end, a small specimen was made, to which the same welding condition for the actual ship structure was applied, to perform fatigue tests. In this study, a method to simply assess changes in welding residual stress according to different static overload was suggested. By measuring actual strain at the weld toe, the weld stress concentration factor and property which is determined by recrystallization in the process of welding were estimated to investigate the relation between overload and fatigue strength.
Study of damage safety assessment for a ship carrying radioactive waste
Lee, Dong-Kon ; Choi, Jin ; Park, Beom-Jin ; Kang, Hee-Jin ; Lim, Suk-Nam ;
International Journal of Naval Architecture and Ocean Engineering, volume 4, issue 2, 2012, Pages 141~150
DOI : 10.3744/JNAOE.2012.4.2.141
Ship damage caused by maritime casualties leads to marine pollution and loss of life and property. To prevent serious damage from maritime casualties, several types of safety regulations are applied in ship design. Damage stability regulation is one of the most important safety issues. Designs of ships for long international voyages must comply with these regulations. Current regulations, however, do not consider the characteristics of the operating route of each ship and reflect only ship size and type of cargo. In this paper, a damage safety assessment was undertaken for a ship carrying radioactive waste in actual wave conditions. Damage cases for safety assessment were constructed on the basis of safety regulations and related research results. Hull form, internal arrangement, loading condition and damage condition were modeled for damage safety simulation. The safety simulation was performed and analyzed for 10 damage cases with various wave heights, frequency and angle of attack on an operating route. Based on evaluation results, a design alternative was generated, and it was also simulated. These results confirmed that damage safety analysis is highly important in the design stage in consideration of the operating route characteristics by simulation. Thus a ship designer can improve safety from damage in this manner.
Mean flow characteristics of two-dimensional wings in ground effect
Jung, Jae-Hwan ; Yoon, Hyun-Sik ; Chun, Ho-Hwan ; Hung, Pham Anh ; Elsamni, Osama Ahmed ;
International Journal of Naval Architecture and Ocean Engineering, volume 4, issue 2, 2012, Pages 151~161
DOI : 10.3744/JNAOE.2012.4.2.151
The present study numerically investigates the aerodynamic characteristics of two-dimensional wings in the vicinity of the ground by solving two-dimensional steady incompressible Navier-Stokes equations with the turbulence closure model of the realizable k-
model. Numerical simulations are performed at a wide range of the normalized ground clearance by the chord length (
) for the angles of attack (
) in the prestall regime at a Reynolds number (Re) of
based on free stream velocity
and the chord length. As the physical model of this study, a cambered airfoil of NACA 4406 has been selected by a performance test for various airfoils. The maximum lift-to-drag ratio is achieved at
and h / C = 0.1. Under the conditions of
and h / C = 0.1, the effect of the Reynolds number on the aerodynamic characteristics of NACA 4406 is investigated in the range of
. As Re increases,
augments and decreases, respectively, and the lift-to-drag ratio increases linearly.
Two-dimensional modeling of stepped planing hulls with open and pressurized air cavities
Matveev, Konstantin I. ;
International Journal of Naval Architecture and Ocean Engineering, volume 4, issue 2, 2012, Pages 162~171
DOI : 10.3744/JNAOE.2012.4.2.162
A method of hydrodynamic discrete sources is applied for two-dimensional modeling of stepped planing surfaces. The water surface deformations, wetted hull lengths, and pressure distribution are calculated at given hull attitude and Froude number. Pressurized air cavities that improve hydrodynamic performance can also be modeled with the current method. Presented results include validation examples, parametric calculations of a single-step hull, effect of trim tabs, and performance of an infinite series of periodic stepped surfaces. It is shown that transverse steps can lead to higher lift-drag ratio, although at reduced lift capability, in comparison with a stepless hull. Performance of a multi-step configuration is sensitive to the wave pattern between hulls, which depends on Froude number and relative hull spacing.
Preliminary tests of a damaged ship for CFD validation
Lee, Sung-Kyun ; You, Ji-Myoung ; Lee, Hyun-Ho ; Lim, Tae-Gu ; Rhee, Shin-Hyung ; Rhee, Key-Pyo ;
International Journal of Naval Architecture and Ocean Engineering, volume 4, issue 2, 2012, Pages 172~181
DOI : 10.3744/JNAOE.2012.4.2.172
One of the most critical issues in naval architecture these days is the operational safety. Among many factors to be considered for higher safety level requirements, the hull stability in intact and damaged conditions is the first to ensure for both commercial and military vessels. Unlike the intact stability cases, the assessment of the damaged ship stability is very complicated physical phenomena. Therefore it is widely acknowledged that computational fluid dynamics (CFD) methods are one of most feasible approaches. In order to develop better CFD methods for damaged ship stability assessment, it is essential to perform well-designed model tests and to build a database for CFD validation. In the present study, free roll decay tests in calm water with both intact and damaged ships were performed and six degree-of-freedom (6DOF) motion responses of intact ship in regular waves were measured. Through the free roll decay tests, the effects of the flooding water on the roll decay motion of a ship were investigated. Through the model tests in regular waves, the database that provides 6DOF motion responses of intact ship was established.