• Journal of the Society of Naval Architects of Korea
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• v.39 no.2
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• pp.1-10
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• 2002

Hull-propeller-rudder interactions are studied by the iterative computational procedures. Hull effects on the propeller are reflected through the effective velocities computed by the vortex ring method which used the measured nominal wake as input data. A potential based panel method has been developed to solve the propeller-rudder interactions using the obtained effective velocities. Steady flow characteristics around the rudder surface can be obtained by computing the induced velocities on the rudder by the propeller and vice versa are computed by the iterative manner until the converged solutions are obtained. Flow characteristics around the propeller and the rudder are measured by Laser Doppler Velocimetry(L.D.V.) in large cavitation tunnel at Samsung Heavy industries. The gap flow model is adopted to solve the characteristics of the horn rudder. Numerical results are compared with the experimental values and the computed velocity fields and pressure distributions with rudder angle on the horn rudder surface show good agreement with measured ones in large cavitation tunnel.

• Journal of the Society of Naval Architects of Korea
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• v.44 no.2 s.152
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• pp.101-110
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• 2007

Recently, rudder erosion due to cavitation frequently has occurred at large high speed container carriers. Especially, in the case of a horn-type rudder, the rudder erosion is severe around a gap. The gap-flow characteristics are investigated through a computational method to understand the effects of a gap on the cavitation and rudder efficiency. A viscous flow theory utilizing a cavitation model is applied to calculate the flow around idealized 2-dimensional rudder sections in a full scale. The effects of gap clearance and flow-control projection are also investigated. From the computational results, the mass flow rate through a gap is found to be one of the important parameters to affect the cavitation and rudder efficiency.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.11
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• pp.1672-1678
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• 2022

In this paper, the relay antenna was designed in consideration of the performance of the 28GHz band 5G mobile communication relay horn antenna, such as radiation pattern and return loss. A horn array for 5G mobile communication repeater was designed by arranging the antenna elements in phase, and the performance was analyzed. Unlike conventional WCDMA (3G) and LTE (4G), in millimeter wave band communication, high path loss occurs between transmission and reception. In the design of a 5G millimeter wave horn antenna, antenna performance such as isolation and gain between antenna elements as well as gain and bandwidth of the antenna must be additionally considered. The antenna gain of the single horn antenna (1×1) and the array horn antenna (2×4) in the 28GHz band is about 10.44d Bi and 19.58dBi, respectively, and the return loss is designed to be less than -18dB. It has proven its validity and has been shown to be suitable for application to 5G mobile communication relay system.

• Journal of the Society of Naval Architects of Korea
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• v.43 no.5 s.149
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• pp.578-585
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• 2006

Cavitation related erosion damages on semi-spade rudder generally occur at around leading edge of lower-face and behind gap of lower pintle. To get the idea of gap entrance profile for the latter case, a series of tests with large models has been carried out at MOERI. In the tests, the flow pattern around lower pintle have been investigated and visualized by high speed camera. Additionally, cavitation inception tests and pressure measurements have also been conducted for better comparison. As a result a new model (F rudder) has been developed. The new model turned out to have stable pressure distribution along the surface and so the cavitation inception speeds within ${\pm}5^{\circ}$ of rudder angle were delayed approx. 4 knots in average.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.4
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• pp.543-552
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• 2010

The Coanda effect is noticeable when a jet stream is applied tangential to a curved surface since then the jet stream remains attached to the surface beyond the point where flow separates otherwise and results in augmentation of circulation and lift. Numerous experimental and numerical studies have been performed in various fields of aerodynamics to exploit the Coanda effect and many of them found to be useful. It can be speculated that the Coanda effect may have practical application to the field of marine hydrodynamics as well since various control surfaces are being used to control behaviors of ships and offshore structures. In the present study, the Coanda effect has been applied to a horn type rudder and a series of numerical computations and model experiments are performed to find the practical applicability. The results indicate that the Coanda jet increases the lift coefficient of the rudder as much as 52% at the momentum coefficient $C_j$ = 0.1 and the rudder angle ${\alpha}=10^{\circ}$.

• Journal of the Society of Naval Architects of Korea
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• v.44 no.3 s.153
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• pp.228-237
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• 2007

The flow characteristics around a horn-type rudder behind an operating propeller of a high-speed large container carrier are studied through a numerical method in fully wetted and cavitating flow conditions. The computations are carried out in a small scale ratio of 10.00(gap space=5mm) to consider the gap effects. The Reynolds averaged Navier-Stokes equation for a mixed fluid and vapor transport equation applying cavitation model are solved. The axisymmetry body-force distribution technique is utilized to simulate the flow behind an operating propeller. The gap flow, the three-dimensional flow separation, and the cavitation are the flow characteristics of a horn-type rudder. The pattern of three-dimensional flow separation is analyzed utilizing a topological rule. The various cavity positions predicted by CFD were shown to be very similar to rudder erosion positions in real ship rudder. The effect of a preventing cavitation device, a horizontal guide plate, is also investigated.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.3
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• pp.238-246
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• 2008

In the present study, the influences on the gap cavitaiton of the semi-spade rudder are investigated experimentally in the condition with propeller and hull wakes. To reduce the scale effect in the given experimental conditions, 1/28.5-scale-down models of propeller and rudder are manufactured. We have the propeller rotate ahead of the rudder, inducing the three dimensional effects originated from the propeller action. Experimental methods are composed of the cavitation observation using high speed camera, PIV (particle image velocimetry) measurements to visualize the cavitaition and flows around the gap. The propeller slipstream affects both of the gap flows and cavitation of the rudder.

• Industry Promotion Research
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• v.8 no.1
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• pp.119-134
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• 2023

An Analysis of the Choice of Wedding Time Based on the Gimundungap Theory. The purpose of this study is to research the utility and validity of wedding time selection based on the principles of Ungokgimun, a recent development of Gimundungap theory. Unlike the conventional way of choosing from common auspicious hours and days deemed available for important ceremonial occasions, Ungokgimun determines the propitious heavenly wedding time catered for a particular couple based on the birth table consisting of the four pillars of the bride- and groom-to-be. Using the Hong Guk-soo numbers which are drawn from the basic principles of oriental philosophy, it utilizes a deductive approach to wedding time choice, which is considered decisive and logical. Wedding time selection for a bride and a bridegroom is determined by auspicious combinations of matching and supporting HongGuk-soo numbers. Some relevant determining factors for the time choice are three number combination of samhap, two number combination of half-hap, latitudinal combination of yuk-hap, support and control relationships between related elements, two number punishment of hyung-sal, and three number punishment of samhyung-sal, etc. The specific auspicious palace of the spouse-to-be's luck is selected on the basis of supporting or brotherly combination of numbers which are manifested on the baseline earthly plate of the bride- and groom-to-be. This is followed by the selection of the ten-year luck, and year and month luck, and finally by the selection of auspicious day and hours. The validity of this study was verified through theoretical consideration of the Ungokgimun and practical analysis of a variety of marriage cases. It was found that the way of wedding time selection using Ungok Gimundungap was relatively more effective than other conventional methods.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.5
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• pp.84-90
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• 2018

When producing a plastic horn cover for an automobile, since the interval between the ribs on the inner surface is narrow, conventional cooling channels cannot be applied and cooling of the mold is difficult. For this reason, the molding operation cannot be completed within a set cycle time. In this study, a conformal cooling channel was applied on the mold to solve the cooling problem. Injection molding simulation was carried out to confirm the effectiveness of the conformal cooling channel. In the analysis results, the mold temperature at the rib section decreased by 33%, and the mold temperature also decreased by 31%. This reduction in temperature allowed for molding within a set cycle time and demonstrated the effectiveness of the conformal cooling channel.

• Special Issue of the Society of Naval Architects of Korea
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• 2009.09a
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• pp.47-51
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• 2009

It is well known that a rudder is influential devices to help ship maintain its stable performances, such as a course-keeping and maneuverability. In the procedures of a commercial ship design proper rudder dimensions (area and shape) ensuring better ship maneuverability have been settled in an initial concept design stage performed by a preceding department, without little structural consideration. It is true that there are time discrepancy between an initial design and a structural analysis stage. Therefore structural analysis results would sometimes cause a rudder to modify its dimensions. Most of these cases, however, ship design and performance tests had been finished. In this matter, only limited modifications of redder could be carried out. Besides, these could also cause bad effects on productivity. Finally, it is necessary to develop a new program considering co-relationship between an initial rudder design and a following work, a structural strength analysis, in order to enhance productivity and minimize a rate of redesign procedures.