• Title/Summary/Keyword: turbulent buoyant jet

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Simultaneous Measurements of Temperature and Velocity Fields of a Buoyant Jet Using LIE and PIV Techniques (LIE와 PIV 기법을 이용한 부력제트의 온도장과 속도장 동시측정)

  • Kim Seok;Jang Young Gil;Lee Sang Joon
    • Proceedings of the KSME Conference
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    • 2002.08a
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    • pp.513-516
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    • 2002
  • The flow structure and heat transfer characteristics of a turbulent buoyant jet were investigated experimentally. The instantaneous temperature and velocity fields in the near field were measured using a two-frame PIV and PLIF techniques. A thin light sheet illuminated a two-dimensional cross section of the buoyant jet in which Rhodamine B was added as a fluorescent dye. The intensity variations of LIF signal from Rhodamine B molecules scattered by the laser light were captured by a CCD camera after passing an optical filter. By ensemble averaging the instantaneous temperature and velocity fields, the mean temperature and velocity fields as well as the spatial distributions of turbulent statistics were obtained. The results show the flow structure and convective heat transfer of the developing shear layer in the near field.

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Theoretical Study on the Behavior of Momentum-controlled Buoyant Jet and Flame of Hydrogen (운동량에 의해 제어되는 수소 부양 제트 및 화염의 거동에 관한 이론적 해석)

  • Yang, Won;Won, Sang-Hee;Kim, Min-Kook;Chung, Suk-Ho;Kim, Jong-Soo
    • Journal of the Korean Society of Combustion
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    • v.10 no.3
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    • pp.34-41
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    • 2005
  • Hydrogen safety is one of the key technical issue with growing attention on utilization of hydrogen energy. This study is aimed to predict behavior of momentum-controlling buoyant jet and flame caused by hydrogen leakage from a high pressured tank. Approximate solutions were derived for the case of turbulent buoyant jet and diffusion flame in still air. In case of hydrogen jet with low Froude number (100-4000), computed jet trajectories were compared with experimental data and showed good agreement with them. Jet and flame trajectories and flame length of hydrogen are predicted and compared with the buoyant flame of propane. The results well show that buoyancy is dominant in the range of low Froude number, while initial momentum is dominant in the range of high Froude number. That effect is more distinct for hydrogen flame than the case of propane.

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Theoretical Study on the Behavior of Momentum-controlled Buoyant Jet and Flame of Hydrogen (운동량에 의해 제어되는 수소 부양 제트 및 화염의 거동에 관한 이론적 해석)

  • Yang, Won;Kim, Jong-Soo;Won, Sang-Hee;Kim, Min-Kook;Chung, Suk-Ho
    • 한국연소학회:학술대회논문집
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    • 2005.10a
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    • pp.207-214
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    • 2005
  • Hydrogen safety is one of the key technical issue with growing attention on utilization of hydrogen energy. This study is aimed to predict behavior of momentum-controlling buoyant jet and flame caused by hydrogen leakage from a high pressured tank. Approximate solutions were derived for the case of turbulent buoyant jet and diffusion flame in still air. In case of hydrogen jet with low Froude number (100-4000), computed jet trajectories were compared with experimental data and showed good agreement with them. Jet and flame trajectories and flame length of hydrogen are predicted and compared with the buoyant flame of propane. The results well show that buoyancy is dominant in the range of low Froude number, while initial momentum is dominant in the range of high Froude number. That effect is more distinct for hydrogen flame than the case of propane.

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Velocity Field Measurements of a Vertical Turbulent Buoyant Jet Using a PIV Technique (PIV 기법을 이용한 비등온 부력제트의 유동구조에 관한 연구)

  • Sin, Dae-Sik;Yun, Jeong-Hwan;Lee, Sang-Jun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.25 no.5
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    • pp.611-618
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    • 2001
  • The flow characteristics of a turbulent buoyant jet were experimentally investigated using a single-frame PIV system. The Reynolds number based on the nozzle exit velocity and nozzle diameter was about Re=5$\times$10$^3$. The instantaneous velocity fields in the streamwise plane passing the jet axis were measured in the near field X/D <11 with and without the temperature gradient. By ensemble averaging the instantaneous velocity fields, the spatial distributions of mean velocity, vorticity, and higher-order statistics up to third order were obtained. The temperature difference of 10$\^{C}$ does not affect a significant influence to the flow structure in the near field, but the total entrainment rate is increased slightly. The entrainment rate shows a linear variation with the streamwise distance in the region after X/D=5.0.

Temperature Field Measurement of Non-Isothermal Jet Flow Using LIF Technique (레이저형광여기(LIF)를 이용한 비등온 제트유동의 온도장 측정)

  • Yoon, Jong-Hwan;Lee, Sang-Joon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.24 no.10
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    • pp.1399-1408
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    • 2000
  • A 2-dimensional temperature field measurement technique using PLIF (Planar Laser Induced Fluorescence) was developed and it was applied to an axisymmetric buoyant jet. Rhodamine B was used as a fluorescent dye. Laser light sheet illuminated a two-dimensional cross section of the jet. The intensity variations of LIF signal from Rhodamine B molecules scattered by the laser light were captured with an optical filter and a CCD camera. The spatial variations of temperature field of buoyant jet were derived using the calibration data between the LIF signal and real temperature. The measured results show that the turbulent jet is more efficient in mixing compared to the transition and laminar jet flows. As the initial flow condition varies from laminar to turbulent flow, the entrainment from ambient fluid increases and temperature decay along the jet center axis becomes larger. In addition to the mean temperature field, the spatial distributions of temperature fluctuations were measured by the PLIF technique and the result shows the shear layer development from the jet nozzle exit.

Vertical Buoyant Jet in Tidal Water-Stagnant Environment (조석(潮汐)의 영향을 받는 수역(水域)에서 연직상향부력(鉛直上向浮力)? -정지수역(靜止水域)-)

  • Yoon, Tae Hoon;Cha, Young Kee;Kim, Chang Wan
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.6 no.2
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    • pp.93-101
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    • 1986
  • The behavior of a plane buoyant jet discharged vertically upward into a stagnant uniform environment is analyzed by continuity, momentum transport equation by numerical scheme. The governing equations are solved by finite difference method employing stream function and vorticity transport and Prandtl's turbulent model. Results for centerline velocities and temperatures, temperature distribution and flow pattern in receiving environment due to buoyant jet in the range of discharge densimetric Froude number of 4 to 32 show good agreement with published data. Spreading rate and dispersion ratio, which are required in integral type analysis of whole range of buoyant jet and have not been obtained yet, are derived in terms of discharge densimetric Froude number and vertical distance from source.

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Initial Mixing Analysis of Ocean Outfalls Discharged into Density Stratified Flowing Ambients (밀도성층화된 흐름수역으로 방류되는 해양방류관의 초기확산해석)

  • Lee, Jae-Hyeong;Seo, Il-Won
    • Journal of Korea Water Resources Association
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    • v.33 no.2
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    • pp.207-217
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    • 2000
  • A numerical model is applied to analyze the mixing characteristics of an axisymmetric turbulent buoyant jet discharged into flowing stratified ambients. The numerical model is a Gaussian-vortex model which incorporates the effects of the vortex pair known as the representative characteristics of far-field in flowing ambients. Six ocean outfalls that have field data for the initial dilution at the water surface are selected for testing the applicability of the developed numerical model. The comparisons of the observed initial dilutions and the simulated ones show that the developed numerical model could be used for the analyses of the initial mixings induced by the sewage diffuser discharged into the ocean.

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Vertical Buoyant Jet in Tidal Water -Crossflowing Environment- (흐름 수역(水域)에서 연직상향부력(鉛直上向浮力)?)

  • Yoon, Tae Hoon;Cha, Young Kee;Kim, Chang Wan
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.7 no.1
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    • pp.11-22
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    • 1987
  • A plane buoyant jet discharged vertically upward into a crossflow is analyzed by numerical solution of the governing equations of continuity, momentum and constituent transport. The turbulent transport is modelled by the Prandtl's mixing length theory. In the numerical solution procedure, the governing equations are transformed by stream function and vorticity transport, non-dimensionalyzed by discharge velocity, slot width, and parameters representing flow characteristics, and solved by Gauss-Seidel iteration method with successive underrelaxation. The numerical experiments were performed for the region of established flow of buoyant jet in the range of discharge densimetric Froude number of 4 to 32 and in the range of velocity ratio of 8 to 15, which is the ratio of discharge velocity to crossflow velocity. Variations of velocities and temperatures, flow patterns and vorticity patterns of receiving water due to buoyant jet were investigated. Also investigated are the effects of velocity ratio and discharge densimetric Froude number on the trajectories of buoyant jet. Computed are velocities, temperatures and local densimetric Froude numbers along the trajectory of the buoyant jet. Spreading rate and dispersion ratio were analyzed in terms of discharge densimetric Froude number, local densimetric Froude number and distance from the source along the jet trajectory. It was noted that the similarity law holds in both the profiles of velocity and temperatures across the jet trajectory and the integral type analysis of Gaussian distribution is applicable.

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Characteristics of an Entrainment into the Turbulent Buoyant Jet in a Cross Flow (직교류에서 난류제트로 유입되는 유량에 관한 고찰)

  • Kim, Hyung Min;Kim, Eunpil
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.23 no.3
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    • pp.342-351
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    • 1999
  • A jet injected normally into a cross flow has been found to have the cross section of a horseshoe shape. It occurs by a twin vortex motion in the region downstream of the jet injection. Such a flow is inherently and highly three-dimensional and numerical calculations should play an important role. The three-dimensional momentum equations with buoyancy effect and energy equation are solved to obtain the velocity distributions, center-line trajectories, cross sectional shape and entrainment. The density difference is sufficiently small, so that the Boussinesq approximation is considered to be valid. The SIMPLE algorithm is applied in a staggered grid system of a calculational domain for the numerical method.

Behavior of Non-buoyant Round Jet under Waves (파랑수역에서 비부력 원형 제트의 거동)

  • Ryu, Yong-Uk;Lee, Jong-In;Kim, Young-Taek
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.19 no.6
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    • pp.596-605
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    • 2007
  • The behavior of a non-buoyant turbulent round jet discharging horizontally was investigated experimentally. The instantaneous velocity field of the jet was obtained using the particle image velocimetry (PIV) method and used to calculate the mean velocity field by phase-averaging. This study tested regular waves with a relatively small wave height for a wavy environmental flow. The centerline and cross-sectional velocity profiles were reported to demonstrate the effect of the waves on the jet diffusion in respect of wave height and wave phase. The wave phase effect was studied for three phases: zero-upcrossing point, zero-downcrossing point, trough. From the results, it is found that the centerline velocity decreases and width of the cross-sectional profile increases as the wave height increases. In addition, the self-similarity of the cross-sectional profile appears to break down although the width of each case along the axial distance does not vary significantly. The phase effect is found to be relatively small compared to the wave height effect.