• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.11-14
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• 2006

This study investigates the flow field of multiple-jet measured by hot-wire anemometry. The experiments were classified into two cases; 6- or 7-nozzle located circumferentially in equal interval without or with a central jet. The effect of the number of nozzles the flow field was examined when the Reynolds number based on the nozzle diameter is about $10^4$. Mean Velocity, normal and Reynolds stresses were measured in the downstream of jets. The Tollmien's theory holds far downstream at 48d apart from the nozzle exit especially when a nozzle locates at the center. The general flow characteristics is influenced due to the number of nozzles.

• Journal of Ocean Engineering and Technology
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• v.21 no.6
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• pp.101-106
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• 2007

In this paper, the authors demonstrate a new idea to take the place of the real pressure vessel test, which should be carried out in a high pressure experiment unit before the real sea trial test. The idea is to make a pressure vessel model as a replica of the real pressure vessel test, which can reduce the cost of making a pressure vessel and large pressure experiment unit. The pressure vessel model was designedbased on linear-elastic, buckling equations and Finite Element Analysis. The manufactured pressure vessel model was investigated and monitored while the pressure test was being conducted. After the test, the result and the validity of the pressure vessel model as a replica of the real pressure vessel test was studied.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.2 no.4
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• pp.33-38
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• 1982

A successful operation of underground oil storage cavern depends on water-tightness around cavern by groundwater. If water-tightness is not secured, gas bubbles would leak out and oil would migrate to an adjacent empty cavern. In this research an electrical analogy method was employed to study the influence of shape of cavern on gas leakage and the required natural groundwater level, relative oil level in two neighboring caverns and cavern spacing to prevent oil migration. The results show that gas leakage is prevented from a cavern with a ceiling of large curvature. The required values of factors to curtail the migration of oil are given on a graph.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.3
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• pp.426-434
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• 2000

This paper deals with a generalized similarity solution for the one-dimensional solidification of ternary or higher-order multicomponent alloys. The present approach not only retains the existing features of binary systems such as temperature- solute coupling, shrinkage-induced flow, solid-liquid property differences, and finite back diffusion, but also is capable of handling a multicomponent alloy without restrictions on the partition coefficient and microsegregation parameter. For an alloy of N-solute species, governing equations in the mushy region reduce to (N+2) nonlinear ordinary differential equations via similarity transformation, which are to be solved along with the closed-form solutions for the solid and liquid regions. A linearized correction scheme adopted in the solution procedure facilitates to determine the solidus and liquidus positions stably. The result for a sample ternary alloy agrees excellently with the numerical prediction as well as the reported similarity solution. Additional calculations are also presented to show the utility of this study. Finally, it is concluded that the present analysis includes the previous analytical approaches as subsets.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.7
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• pp.569-574
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• 2014

In order to investigate low frequency swishing noise of wind turbines, acoustic source model using a singularity in circular motion is introduced to derive analytic solution of Lowson acoustic analogy in time domain. Results in time and frequency domains computed by the solution show apparent modulation of amplitude and frequency. The solution indicates that time histories of acoustic pressure at receiver points varied significantly according to receiver's directional location, even when the retarded time distributions are similar. However, the corresponding time-averaged spectra of sound pressure at the receiver locations where the retarded time distributions are almost same are not significantly different. It can be inferred from these results that the time-averaged sound pressure spectra which cannot take into account the detailed difference in the time-variation of wind turbine noise may not represent the sound quality of wind turbines due to its swishing. Finally, as an introduction of procedure to quantify low frequency swishing noise level, relative variation of overall sound pressure level is obtained using tonal low frequency noise model.

• 프린팅코리아
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• s.2
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• pp.36-37
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• 2002

지난 6.13 지방선거에 총 10명의 인쇄인이 당선됐다. 총 24명이 의회 진출을 시도한 가운데 광역의원 선거에선 6명이 도전해 3명이 당선됐으며, 기초의원선거에선 총 18명이 나서서 7명이 당선의 기쁨을 누렸다. 시, 도의원 당선자는 인천 중구 제1선거구의 안병배(진문사인쇄소.45세), 충남 연기군 제1선거구 유환준(일신인쇄사.56세), 전북 무주군 무주제1선거구 윤완병(현대인쇄광고.46세) 의원등 이다. 구, 시, 군의원 당선자는 서울 도봉구 창제5동 목충균(세로와상사.62세), 서울 송파구 거여제1동 장경선(이레문화사.61세), 부산 중구 중앙동 영주1동 김만택(한일인쇄.58세), 부산 동래구 사직제1동 강신두(영남종합인쇄.48세), 대구 북구 침산3동 김형구(경원인쇄소.60세), 충남 보령 대천1동 임대식(명문당인쇄소.52세), 경북 경주시 동천동 김병태(경주인쇄소.44세) 의원 등이다. 새로이 의회에 발을 들여놓은 이들은 이구동성으로 인쇄업 경영이 선거에서 크나큰 도움이 됐다고 말했다. 당선자 모두는 인쇄업을 직접 경영한 경우였으며, 후보자 가운데는 광역의회와 기초의회 각각 1명씩 2명의 인쇄 현장 근로자들도 있었으나 탈락의 고배를 마셨다. 6.13 지방선거에 출마해 당선돼 인쇄업의 위상을 한층 드높인 대표 당선자 인터뷰와 10명 당선자들의 인적 사항을 정리했다.

• Journal of Korea Water Resources Association
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• v.30 no.6
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• pp.611-620
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• 1997

The history of Tidal Bench Mark(TBM) at four major tide observation stations on the the Korea West Coast is reviewed. The data concerned with the local mean sea level(LMSL), the datum level(DL), and TBM is collected and checked. The values of LMSL surveyed by Rural Development Corporation(RDC), Office of Hydrographic Affair(OHA), and Office of Port Affair(OPA) are compared so that their unbiased MSLs at four stations are determined. Kriging model is introduced to estimate the design levels for tide; DL, MSL, and high water spring tide(HWOST). The estimated design level is well fitted with the sample data. The value of the identified drifts increase with the latitude. The estimated semi-variograms ${\gamma}(h)$ show self similarity. The values of the ${\gamma}(h)$ for DL and HWOST are 0.005 times as much as the values of ${\gamma}(h)$ of MSL.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.3
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• pp.259-268
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• 2012

This study measured the natural-convection heat transfer of two vertically staggered cylinders with varying vertical pitch-to-diameter ($P_v$/D) and horizontal pitch-to-diameter ($P_h$/D) ratios. The measured heat-transfer rates for the lower cylinder agreed well with the existing heat-transfer correlations for a single cylinder. At the smallest $P_v$/D, the rising plume from the lower cylinder provides the upper cylinder with a preheated flow, and the heat-transfer rates of the upper cylinder decrease, but increase very sensitively with $P_h$/D. However, at the largest $P_v$/D, the velocity effect dominates, and the heat-transfer rates of the upper cylinder are larger than that of a single cylinder, and decrease less sensitively with $P_h$/D. Even if $P_h$/D is increased, the heat-transfer rate of the upper cylinder is higher than that of the lower cylinder because of the chimney and side flow effects. This work expanded the flow ranges to turbulent flows. The cupric acid-copper sulfate ($H_2SO_4-CuSO_4$) electroplating system was adopted for the measurements of the mass-transfer rates instead of the heat-transfer experiments based on the analogy concept. The measurements were made by varying $P_v$/D (1.02-5) and $P_h$/D (0-2) in both laminar and turbulent flows. The Rayleigh number ranged from $1.5{\times}10^8$ to $2.5{\times}10^{10}$, and the Prandtl number was 2,014.

• Journal of Energy Engineering
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• v.21 no.1
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• pp.18-25
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• 2012

This work investigated the influence of the chimney dimensions(exit and entrance length, and diameter) on the heat transfer of a vertical cylinder in a duct. The measured mass transfer rates for the natural convection of vertical cylinder in a duct were presented for Prandlt number 2,094, Rayleigh number in the range of $4.55{\times}10^9$, $5.79{\times}10^{10}$, and $1.69{\times}10^{11}$. Experiments were performed using a copper sulfate electroplating system to simulate heat transfer based upon the analogy concept. The diameter of the duct was varied from 0.06 m to 0.14 m, and the heights from 0.30 m to 1.10 m. Nusselt numbers measured at open channel condition agreed well with the existing laminar heat transfer correlations for vertical plate developed by Le Fevre. The increase of the exit length enhanced the heat transfer up to a certain duct height but further increase does not affects the heat transfer. The heat transfer decreased with increasing the entrance length up to a certain duct height and was constant at further increase. The Nusselt number decreased with increasing the diameter of duct, until Nusselt number becomes similar to that at open channel beyond a certain diameter.

• Journal of Energy Engineering
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• v.20 no.3
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• pp.242-251
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• 2011

The effects of top and bottom lids on the natural convection heat transfer phenomena inside vertical cylinders were investigated experimentally for $Ra_{Lw}$ from $9.26{\times}10^9$ to $7.74{\times}10^{12}$. Using the concept of analogy between heat and mass transfer, a cupric acid-copper sulfate electroplating system was employed as mass transfer experiments replacing heat transfer experiments. The natural convection heat transfer of both-open cylinders in laminar and turbulent flows was in good agreement with the existing heat transfer correlations developed for vertical plates. The effects of top and bottom lids on the heat transfer rates were very similar to the studies of Krysa et al. and Sedahmed et al. and Chung et al. With the copper lids, the bottom-closed cavity showed the highest heat transfer rates and then followed both-closed, top-closed, both-open ones in both laminar and turbulent flows. However with the acryl lids, the similar trends were observed except that the heat transfer rates for both-open were higher than top-closed one. The use of the copper lids increased the heat transfer rates compared to the acryl lids due to the hydrodynamic interaction of the flows developed for the different heated faces. This study extended the ranges of flow conditions of the existing literatures and proposed the empirical correlations.