• Title/Summary/Keyword: 이중확산 유동

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Double-Diffusive Convection in Molten Pb-Sn Alloy (용융상태인 납-주석 합금의 이중확산유동)

  • ;Bergman, T. L.
    • Journal of Advanced Marine Engineering and Technology
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    • v.19 no.2
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    • pp.27-35
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    • 1995
  • 액체 상태인 Pb-Sn 합금에 의한 이중확산유동에 대해 체비세프 콜로케이션 기법을 이용하여 수치해석하였다. 온도차에 의한 부력과 농도차에 의한 부력이 작을때에는 유동형태가 서서히 준정상상태에 이르러 아무런 진동현상을 볼 수 없다. 부력이 증가함에 따라 유동은 수직 농도 경계층을 파괴하여 플륨(Plume)형태의 유동을 생성시키고, 이는 시스템 내부로 성장한 후 소멸된다. 이러한 현상이 반복되면서 높은 주파수의 진동현상을 관찰할 수 있다.

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URANS Computations for Flow Mixing of Heated Dual Jets (URANS를 이용한 가열된 이중제트의 유동혼합 특성에 대한 수치해석)

  • Park, Tae Seon
    • Journal of the Korean Society of Propulsion Engineers
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    • v.23 no.3
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    • pp.18-27
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    • 2019
  • The flow mixing characteristics for the heated dual jets were numerically studied by using URANS (unsteady Reynolds-averaged Navier-Stokes). The increased turbulent diffusion was obtained for the compressible flow, and the thermal diffusion of incompressible flow increased more than that of compressible flow. From the results of FFT and phase portraits, periodic and quasi-periodic states were observed as the jet spacing increased. It was observed that linear variations of merging points and combined points were different because unsteady flow determined the flow mixing characteristics for a large jet spacing.

Nemerical Analysis of Natural Convection in a Confined Stratified Fluid (밀폐용기내 성층화된 유체의 자연대류에 관한 수치적 연구)

  • 현명택;이진호;모정하
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.13 no.6
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    • pp.1321-1329
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    • 1989
  • 본 논문에서는 성층화된 용액ㅇ네 수평방향으로 온도구배가 가해지는 경우에 있어서 두 부력인자의 상대적 크기에 따라 나타나는 유동형태와 그에 따른 온도, 농도 분포 및 열전달특성을 수치적으로 연구하고자 한다.

Numerical Study on Double-Diffusive Convection in a Stratified Trapezoidal Enclosure (성층화된 사다리꼴 용기내에서의 이중확산유동에 관한 수치해석)

  • 현명택
    • Journal of Ocean Engineering and Technology
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    • v.6 no.2
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    • pp.143-150
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    • 1992
  • Numerical simulation is made of a stably stratified salt-water solution due to lateral heating in an equilateral trapezoidal enclosure using boundary-fitted coordinate in grid generation. Results show four types of the global fluid pattern depending on the buoyancy ratio in the enclosure, i.e., unicell flow pattern for the low buoyancy ratio, layered flow pattern for the increasing buoyancy ratio, layered flow pattern with stagnant zone for the relatively high buoyancy ratio and stagnant flow pattern for the much higher buoyancy ratio.

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Experimenal Study on Unsteady Double-Diffusive Convection in a Rectangle (사각형 용기내의 비정상 이중확산유동에 관한 실험적 연구)

  • 홍남호;김창수;현명택
    • Journal of Ocean Engineering and Technology
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    • v.8 no.1
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    • pp.105-113
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    • 1994
  • Double-diffusive convection induced by simultaneously-imposed lateral temperature and concentration gradients in a rectangular enclosure with aspect retio, 2.0 has been studied experimentally for adiabatic and isothermal horizontal boundary conditions. Visual observations show two distinct flow structures depending on the buoyancy ratio. The unicell flow structure is observed for a lower buoyancy ratio while the layered flow structure appears for a higher buoyancy ratio. There exists an unstable flow regime between two buoyancy ratios.

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Thermal-flow Characteristics of Magnetic Fluid for Concentric Annuli Under Fixing Magnetic Field Using Visualization Technique (가시화기법을 이용한 고정자장에서 이중원관내 자성유체의 열유동 특성에 관한 연구)

  • Kim, Hyung-Jin;Seo, Jae-Hyeong;Kim, Dae-Wan;Lee, Moo-Yeon;Seo, Lee-Soo
    • Journal of the Korean Magnetics Society
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    • v.23 no.1
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    • pp.26-30
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    • 2013
  • This article is experimentally to investigate thermal-flow characteristics of the magnetic fluid for concentric annuli under externally fixed magnetic fields using visualization technique. Temperatures of the inner tube and outer tube in the tested concentric annuli were constantly maintained at both $30^{\circ}C$ and $25^{\circ}C$ and the middle tube was filled with the magnetic fluid. Magnetic field was uniformly applied using 4 permanent magnets at 4 directions of the concentric annuli. As a result, the thermal-flow characteristics of the magnetic fluid for concentric annuli could be controlled by directions of the external magnetic fields.

Effects of Combustor Configuration on the Stability of Supersonic Turbulent Lifted Flame in a DCR Engine (이중 연소 램제트 엔진에서 연소기 형상에 따른 초음속 난류 부상 화염의 안정성 연구)

  • Choi, Jeong-Yeol
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2011.11a
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    • pp.595-598
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    • 2011
  • Supersonic combustion phenomena in the main combustor of a dual combustion ramjet (DCR) engine are studied numerically. Since the supersonic combustion is affected significantly by the compressibility effects parametric studies have been carried out for the constant are length and the divergence angle. Numerical studies with fixed inflow condition for different geometric configurations reveals that the supersonic combustion in DCR combustor has the characteristics of lifting flame, where the lifting flame is maintained near the injector tip for the case of long combustor length with small divergence angle, but the lifting height is significantly increase for large divergence angle resulting flame blow-out of the combustor. Therefore, it is concluded that flame stability should be considered sufficiently in the design o DCR combustor.

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Double Diffusive Convection of a Stratified Fluid in a Rotating Annulus Due to Lateral Heating (환형용기내 성층화된 유체의 회전효과에 따른 이중확산대류에 관한 실험적 연구)

  • 강신형;전창덕;이진호
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.7
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    • pp.1709-1719
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    • 1995
  • The primary objective of the paper is to obtain the basic information of the natural convection of a stratified with various parametric conditions related to rotating speed, temperature and concentration gradient. For the purpose of it, experiments are performed in a stably stratified salt-water solution with lateral heating in a stationary or rotating annulus. The experiment covers the ranges of Ar=2, Le=100, R $a_{\ta}$=2 10$^{5}$ and Ta=0, 10$^{5}$ - 2.5*10$^{8}$ . Many interesting flow phenomena are observed and rotation effects are examined. Particularly as Taylor number increases (rotation increases) at a given R $a_{\ta}$, the generation of rolls at hot wall is inhibited and the formation and merging process of layers are delayed.

Numerical Analysis of Fully Developed Turbulent Recirculating Flow and Heat Transfer for The Periodic Variations of Cross Sectional Area (周期的으로 斷面이 變化하는 完全確立된 亂流再循環 流動과 亂流熱傳達의 數値分析)

  • 이병곤;최영돈
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.10 no.1
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    • pp.138-149
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    • 1986
  • A numerical method is developed for the solution of fully developed turbulent recirculating flow whose cross-sectional area varies periodically. This enalbes the flow field analysis to be confined to a single isolated module, without involvement with the entrance region problem. This method are applied to the analysis of the turbulent flow field and heat transfer in artificially roughened annulus with repeated square rib.

Modeling of thermal fluidized desorption for diesel-oil contaminated soils (Diesel-oil에 오염된 토양의 유동상 열탈착 모델링)

  • 이상화;김병욱;이상득;박달근;이중기
    • Journal of Korea Soil Environment Society
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    • v.4 no.2
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    • pp.137-147
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    • 1999
  • Fluidized-bed thermal desorber coupled with a heat pipe was investigated for the remediation of soil contaminated with diesel oils. Thermal gravimetric analysis by Cahn-balance indicated that the desorption of diesel oils from the soil particles was mainly governed by the internal diffusion at low concentration of less than 0.5 wt. % of oils in the soil particles. In fluidized-bed experiments. increase of fluidizing gas velocity reduced the residual oils of the contaminated soils, the increase of soil feed rate decreased efficiency of fluidized-bed desorber. A mathematical model was developed by incorporating Fickian diffusion kinetics into the Kunii-Levenspiel model Simulation results showed reasonable agreement for the performance of fluidized-bed thermal desorber.

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