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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
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Journal DOI :
The Society of Naval Architects of Korea
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Volume & Issues
Volume 35, Issue 4 - Nov 1998
Volume 35, Issue 3 - Aug 1998
Volume 35, Issue 2 - May 1998
Volume 35, Issue 1 - Feb 1998
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An Implicit Numerical Method for Two-Dimensional Tidal Computation
Sun-Young Kim ; Mu-Seok Song ;
Journal of the Society of Naval Architects of Korea, volume 35, issue 1, 1998, Pages 1~14
A two-dimensional numerical model for tidal currents based on the depth averaged equation is developed. The mode1 employs a rectangular grid system for its simplicity in the application of complicate coastal shore lines. To raise computing efficiency, implicit approximate factorization scheme is implemented in solving governing equations. An upwind-differencing is used to discretize convective terms, which provides a numerical dissipation automatically and suppresses any oscillations caused by nonlinear instabilities. Some numerical tests are made against the analytic solutions of a linearized shallow water equation to validate the developed numerical scheme, and comparisons of the model prediction with the analytic solution are satisfactory. As a real application, the tidal currents are computed on the Inchon area where the tidal currents are important for the design of new canal which is under construction.
Numerical Investigations on Vortical Flows and Turbulence beneath the Free Surface around Bow
Uh-Cheul Jeong ; Yasuaki Doi ; Kasu-hiro Mori ;
Journal of the Society of Naval Architects of Korea, volume 35, issue 1, 1998, Pages 15~23
Characteristics of turbulence beneath the free surface around a blunt bow are numerically-investigated. Three dimensional wavier-Stokes and continuity equations are solved for the simulations.. The Large Eddy Simulation(LES) with the external disturbance is performed to simulate the turbulent free surface flow called sub-breaking wave. The result shows that the free surface fluctuates beyond a certain critical condition and the characteristics of the fluctuation are similar to the turbulent boundary layer flow around a solid body.
The Effect of Trailing Wake Asymmetry on a Propeller Blade Forces in Inclined Inflow
Sang-Woo Pyo ;
Journal of the Society of Naval Architects of Korea, volume 35, issue 1, 1998, Pages 24~31
Unsteady propeller blade forces arising from shaft inclination have been found to be an important contribution tn total blade forces. The position of the wake relative to a blade oscillates with the first blade frequency, thus giving rise to unsteady blade forces which is significant relative to the forces produced directly by flow inclination. In order to find a wake geometry due to shaft inclination, a non-axisymmetric wake model is developed and applied to a specific case, which has experimental values. Predicted cavity shapes and unsteady forces acting on the blades of an inclined shaft propeller are compared to those predicted by other numerical methods, as well as those measured in experiments.
A Study on Nonlinear Motions of Submerged Circular Cylinder in Regular Wave
Ho-Young Lee ; Jong-Heul Hwang ;
Journal of the Society of Naval Architects of Korea, volume 35, issue 1, 1998, Pages 32~39
A numerical analysis for large amplitude motions of submerged circular cylinder is presented. The method is based on potential theory and two-dimensional motions in regular harmonic waves are tented as an initial value problem. The fully nonlinear free surface boundary condition is assumed in an inner domain and this solution is matched along an assumed an assumed common boundary to a linear solution in outer domain. Calculations of the large amplitude motion of a submerged circular cylinder are directly simulated in time domain. It is shown that relative motion between the body and fluid particle gives a significant effect on the lift and drift motions.
A Study on the Assessment for the Auto-pilot System of a Ship in Waves
S.K. Lee ; K.W. Lee ; T.K. Kim ;
Journal of the Society of Naval Architects of Korea, volume 35, issue 1, 1998, Pages 40~45
There are two kinds of methods in the analysis of ship motion in irregular waves. The one is the spectral method in which the ship motion is assessed with spectral of irregular waves times R.A.O. of a ship. The other is, so called, time domain analysis, in which the irregular waves are used directly in the equation of ship motion to calculate the responses. In this paper, both methods are applied for the calculation of course keeping motion of a ship in irregular waves with auto-pilot control. And, the differences and useful1ness of the two methods in the assessment of auto-pilot system are compared.
Improvement of Prediction Technique of the Ship′s Manoeuvrability at Initial Design Stage
Ho-Young Lee ; Sang-Sung Shin ; Deuk-Joon Yum ;
Journal of the Society of Naval Architects of Korea, volume 35, issue 1, 1998, Pages 46~53
In this paper, we studied to improve Inoue's and Kijima's model used to predict ship's manoeuvrability at initial design state. To perform this work, we carried out PMM(Planar motion Mechanism) test and rudder open water test for 12 models of low-speed blunt-ship which have horn type rudders and bulbs in afterbody. As we adopted MMG(Mathematical Modelling Group) model, we could analyze hydrodynamic and MMG experimental coefficients. The regression analyses by principle parameters were carried out for hydrodynamic and MMG experimental coefficients. The regression analyses by principle parameters were carried out for hydrodynamic and MMG experimental coefficients and the equations by regression analysis wee used to search sensitivities and to estimate ship's manoeuvrability. We had simulated ship's manoeuvrability to check revised MMG.
Evaluation of Course-keeping Quality of a Ship by Zig-Zag Test
Seung-Keon Lee ; Seung-Jae Lee ;
Journal of the Society of Naval Architects of Korea, volume 35, issue 1, 1998, Pages 54~60
Generally, spiral test has been used for evaluating course-keeping quality of a ship. But, there are many difficult problems in performing spiral test and reversed spiral test. Therefore, we propose zig-zag test instead of spiral test for evaluating curse-keeping quality of a ship. In this paper, K-T maneuvering response model is applied to the spiral curves which are systematically produced to calculate Zig-zag maneuver. Then, 1st overshoot angle and 2nd overshoot angle are plotted. And the relations between overshoot angles and band widths of spiral curve are discussed.
Development of Elastic-Plastic Fracture Analysis Program for Structural Elements under an Impact Loadings
K.S. Kim ; J.B. Park ;
Journal of the Society of Naval Architects of Korea, volume 35, issue 1, 1998, Pages 61~71
This paper describes a dynamic fracture behaviors of structural elements under elastic or elasto-plastic stress waves in two dimensional space. The governing equation of this problem has the type of hyperbolic partial differential equation, which consists of the equation of motions and incremental elasto-plastic constitutive equations. To solve this problem we introduce Zwas' method which is based on the finite difference method. Additionally, in order to deal with the dynamic behavior of elasto-plastic problems, an elasto-plastic loading path in the stress space is proposed to model the plastic yield phenomenon. Based on the result of this computation, the dynamic stress intensity factor at the crack tip of an elastic material is calculated, and the time history of a plastic zone of a elasto-plastic material is to be shown.
Dynamic Responses of a Rigid-Plastic Cantilever Subject to Impact
H.W. Choi ; J.G. Shin ;
Journal of the Society of Naval Architects of Korea, volume 35, issue 1, 1998, Pages 72~79
Static deformation theory of elastoplastic structures can be applied only if the magnitude of loading is less than the plastic collapse force
. However, with impact or explosive blast loading, the structure can be subjected to an intense but short-duration force pulse that exceeds the plastic collapse force and initiates structural collapse. In this paper, the dynamic response of a rigid-perfectly plastic cantilever subject to intense impact loading is examined in terms of the plastic collapse force. When a step loading is applied, the motion of the beam is calculated and analyzed through the non-dimensionalization of variables. It is concluded that the motion of a beam can be characterized as a function of the nondimensionalized force parameter,
represents the critical force for plastic collapse. This result is used to the analysis of the beam motion subject to rectangular force pulse.
Fatigue Strength Analysis of Marine Propeller Blade to Change in Skew Angle
Bal-Young Kim ; Joo-Sung Lee ;
Journal of the Society of Naval Architects of Korea, volume 35, issue 1, 1998, Pages 80~87
This paper deals with the evaluation of structural safety to fatigue strength of marine propeller blades having high skew angle and operating in irregular wake field. The determination of the optimum skew angle of a propeller blade is one of the important task at the initial design stage especially in the case of high speed vessel such as container ships. A computer program system has been developed to evaluate the structural safety to fatigue strength and has been applied to several propeller blades with varying skew angle within a wide range. In the parametric study the pressure acting on the blade surface is calculated using the non-lineal lifting surface theory and the structural analysis is performed using MSC/NASTRAN. The relationship between skew angle and structural safety to fatigue strength is investigated and this paper ends with describing the optimum skew angle of a propeller blade.
A Study on the Optimum Design and Structural Behaviors of Aluminium Extrusions
S.I. Seo ; K.H. Son ;
Journal of the Society of Naval Architects of Korea, volume 35, issue 1, 1998, Pages 88~97
Large aluminium extrusions can be used in rolling stocks and high speed vessels to reduce weight and labor cost. As sandwich plates with corrugated core have enough strength in transverse and longitudinal direction, welding lines to connect members are reduced and transverse members to strength longitudinal members are not required. However, for proper design of aluminium extrusion plates, understanding of structural behaviors of the exclusions are necessary. In this paper, at first, detailed finite element analysis is carried out to understand structural behavior. And then, simple theoretical formulas for design purpose are proposed using the orthotropic plate theory. Shear stresses resulting from end twisting which is characteristics of deep aluminium extrusion plates can also be calculated by the simple theoretical formula. Comparison with the results by detailed finite element analysis shows good accuracy of the proposed simple formulas. The simple formulas can be useful in repetitive analysis in the initial design stage.
Heat Flux Calculation for Thermal Equilibrium of Cofferdam in a LNG Carrier
Joo-Ho Heo ; Young-Bum Lee ;
Journal of the Society of Naval Architects of Korea, volume 35, issue 1, 1998, Pages 98~106
This paper shows the temperature distribution of double hull compartment and of cofferdam in a large LNG Carrier. In LNG Carrier, due to the lower cargo temperature(
), structures are forced to lose their strength if additional heat is not supplied. So it is very important to estimate the temperature distribution and the heat flux needed to maintain the structure properly. The temperature of each compartment is obtained using 2-dimensional model analysis and compared with 3-dimensional results. And also this paper gives preliminary estimation of pipe length to supply necessary heat flux in bare pipe and finned pipe.