• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.10
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• pp.1229-1239
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• 1999

A computational study on unsteady compressible flows has been performed by adopting a low Reynolds number $k-{\omega}$ turbulence model in conjunction with dual time stepping scheme. An explicit four-stage Runge-Kutta scheme for the Navier-Stokes equations and an approximate factorization scheme for the $k-{\omega}$ turbulence model equations are used. Computational results obtained for blade surface pressure distributions in the process of rotor-stator interaction in a turbine stage are in good agreement with extant experimental data. The effects of the wake from the stator on the boundary-layer transition over the rotor blade surface are discussed by showing that high intensity turbulence of the stator wake induces an early transition.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.5 no.2
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• pp.51-57
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• 1993

It is often assumed that the wave velocity at the bottom given by potential wave theory il the same as the wave velocity at the top of the turbulent boundary layer. This assumption is found to be the major cause of the error detected by recent elaborate theories and numerical models for the description of velocity profile near the sea bottom. A relationship is suggested between the potential velocity and the real boundary velocity. Based on this relation, the existing theories of Jonsson (1967) and Fredsoe (1984) are refined for the estimation of wave friction factor, and the computation results of the modified theories are favourably compared with the published laboratory results.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2013.11a
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• pp.182-183
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• 2013

FDS(Fire Dynamics Simulator)는 국내에서 화재해석을 위해 사용되고 있는 가장 보편적인 소프트웨어 중의 하나이다. 미국의 NIST에서 25년간 지속적인 업그레이드를 통해 개발되어 오고 있으며 인터넷 상에서 무료로 배포되고 있어 전 세계의 화재관련 연구자 및 학생들이 연구 및 학습의 목적으로 사용하고 긴 기간동안 많은 전문가들에 의해 검증되어온 소프트웨어이다. 하지만 FDS가 난류해석을 위해 사용하고 있는 Smagorinsky의 LES(Large Eddy Simulation)모델은 현재까지 발표된 LES모델 중 가장 초기의 모델로서 건축물과 같이 복잡한 형상을 갖는 계산영역에서는 결과의 신뢰성이 많이 떨어지는 것으로 알려져 있다. 본 연구에서는 FDS의 대공간의 화재해석 성능을 평가하는 것을 목적으로 스페인 Murcia에서 수행된 Murcia Atrium Fire Test를 해석 대상으로 하여 FDS가 사용하고 있는 Smagorinsky의 LES모델 및 3가지의 다른 LES모델을 사용하여 대공간 내부의 연기유동을 해석하였으며 그 결과를 비교하였다.

• 한국연소학회:학술대회논문집
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• 2015.12a
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• pp.267-268
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• 2015

The multi-environment probability density function model has been applied to simulate the turbulent $CH_4/H_2$ flames under MILD conditions. The direct quadrature method of moments (DQMOM) has been adopted to solve the transport PDF equation due to its computational efficiency and robustness. The IEM model represents the micromixing process. The numerical results obtained in this study are precisely compared with experimental data in terms of unconditional means and conditional means for scalar field including temperature and species mass fraction.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.25 no.1
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• pp.65-72
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• 1992

It is believed that the lower cold water is formed by winter cooling in the north of the East(Japan) Sea. To examine its effect on the general circulation of the East Sea, we performed a two-layer numerical model with realistic bottom topography. First a circulation is generated by imposing only an inflow and an outflow which is then modified by adding the cooling effect in the north. The interface between the two layers rises due to cooling and propagates along the coast as internal Kelvin waves. About 7 months after the cooling starts, all coastal areas of the basin have higher elevation than that in offshore region. This induces baroclinic currents resulting in clockwise(anticlockwise) circulation in upper (lower) layer of the basin. It is concluded that the East Korean Warm Current strengthens as a result of lower cold water formation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.12
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• pp.1209-1215
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• 2012

Experiments with premixed flames in a tube have been conducted to investigate the transition phenomenon from a laminar flat flame to turbulent motions. To induce this phenomenon, a flat flame is formed in a tube. Then, the local velocity at the center of the flat flame surface is increased using $CO_2$ laser irradiation. The deformed flame front propagates with an increase in the total flame surface and oscillating instability. Eventually, the flame front accelerates explosively, and it shows turbulent flame motions with a strong noise. The dynamic behaviors of the flame front prior to the turbulent motions are analyzed in this study to elucidate this process. The physical model of the process is presented according to observations.

• Journal of the Korean Society for Marine Environment & Energy
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• v.10 no.1
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• pp.59-65
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• 2007

Rapid variation of coastal ecosystem in the East Sea of Korea, such as fishery resource variation and subtropical chang of bentic flora, accordong to the global warming are actually noticed. In this study we try to identify the characterics of water mass existing in this coastal area and to consider the variation of their physical and chemical properties using data of temperature, salinity and dissolved oxygen obtained by National Fisheries Research & Development Institute from 1960 to 2005. The temperature of all water mass rise during last 45 years; the rise of North Korea Cold Water temperature (about $2.33^{\circ}C$) is 1.5 times higher than that of Tsushima warm water (about $1.6^{\circ}C$), and the temperature rise of Tsushima Surface Water, directly affected by climate chang is $2.57^{\circ}C$, higher than the atmospheric temperature rise during same period, indicating that subtropical change makes progress more rapidly in the coastal marine ecosystem than in the land ecosystem. Otherwise, the salinity in the surface water decrease $0.29\%_{\circ}$ during last 45 years due to the rising trend of rainfall with atmospheric temperature. The dissolved oxygen concentration in the all water mass make a decreasing trend. Specially for the North Korea Cold Water, the dissolved oxygen concentration diminish 0.021 mg/l per year and the decrease in the East Sea Proper Water indicate a change of inner water circulation system.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.2
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• pp.226-244
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• 1998

The relationship between the transport of eggs and larvae of Anchovy (Engraulis japonica) and the oceanic condition in the southern sea of Korea was examined on August and November 1996. In summer (August), when the Tsushima Warm Current is strong near to the coast, the warm waters such as warm streamers from the Tsushima Warm Current intrude into the coastal area, and cyclonic circulations are formed. The warm water intrusions also generate wakes around Komun Island, Sori Island and Koje Island. In the coastal area where the warm water intrusions occur, the nutrients, dissolved oxygen, suspended solid and chlorophyll are concentrated in probably relation to the upwelling concerned with this warm streamer and/or the wakes. Anchovy eggs and larvae are transported to the coastal area by the cyclonic circulations. The hatching and growth of anchovy larvae are increased because of high primary production in the cyclonic circulations. However, as the amount of Copepods which are a main food for anchovy larvae decrease in the coastal area, anchovy larvae seem to move to the Isushima Warm Water area for seeking a prey. In autumn (November), the Tsushima Warm Current is far away from the coast. In this season the warm water intrusions almost disappear, and the small scaled frontal eddies are formed between the coastal water and the Tsushima Warm Water. As the surface water moves towards offshore, few anchovy eggs and larvae were sampled in the survey area. Chemical and biological substances are concentrated in the leftdown sides of the small scaled frontal eddies because of eddy formation.

• 한국연소학회:학술대회논문집
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• 2014.11a
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• pp.185-186
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• 2014

The multi-environment probability density function model has been applied to simulate the turbulent stratified premixed flames. The direct quadrature method of moments (DQMOM) has been adopted to solve the transport PDF equation due to its computational efficiency and robustness. The IEM mixing model is employed to represent the mixing process and the chemical mechanism is based on Gri 3.0 mechanism. Numerical results obtained in this study are precisely compared with experimental data in terms of unconditional and conditional means for scalar fields and velocity fields.

• Journal of the korean Society of Automotive Engineers
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• v.13 no.4
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• pp.11-17
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• 1991

내연기관의 열전달은 구조물에 따라 흡기계통, 연소실, 배기계통으로 나누어지고, 열전달기구에 따라 전도, 대류, 복사로 나누어지며, 여기서는 그중 가장 핵심이 되는 연소실 내에서의 대류 및 복사 열전달 현상에 관하여 논하고자 한다. 연소실 열전달의 정량적 해석을 위해서는 흡기계통과 피스톤 운동에 의한 3차원 압축성 난류 유동장과 점화, 착화 및 연소 진행과정, 이들의 복합적 상호 작용에 대한 이해가 선행되어야 한다. 여기서는 현재까지 제시된 연소실 열전달의 정량적 모델과 문제점,앞으로의 연구 진행방향에 대해 소개하고자 한다.